Installing Office Web Apps: Existing SharePoint 2010 Server Farm

Nice Artcile by Michael Mukalian explained step by step

I just got done doing this a couple times, so I wanted to just throw out there steps with pictures.  The installation process is pretty much from the Deploy Office Web Apps (Installed on SharePoint 2010 Products) TechNet article, but I wanted to show images along with each step.  So, with that said, here we go:
1. Download the Office Web Apps install from wherever you've access to it (it's a seperate download in the MSDN area), and then run setup.exe.
2. Enter your Product Key when asked for it

3. Accept the Software License Terms and click <Continue>

4. Select a file location then click <Install Now>

5. Watch the progress bar scroll :)

6. When the installation completes you'll be prompted to run the Configuration Wizard.  Make sure the checkbox is checked to do so, and click <Close>

7. Click <Next> on the Welcome dialog

8. Click <Yes> in the Service Reset Notification dialog



9. Click <Next> in the Completing dialog

10. Watch another progress bar :)

11. Click <Finish> in the Successful Configuration dialog

12. Alrighty then, the bits are installed so time for configuration...fire up Central Administration from Start --> All Programs --> Microsoft SharePoint 2010 Products --> SharePoint 2010 Central Administration 

 

13. Click the Manage services on server link in the System Settings section>

 

14. You'll note in the Services page that there are now instances of the services that represent the ones necessary for Office Web Applications.  These will need to be started up.  Click Start on each one to start them up.
      - Note: When installing Office Web Apps in a multi-server environment, these will need to be started on each server that you choose to run them on.>

 

15. Now that the instances are started up, we'll need to create the service spplications, and their proxies, thereby wiring up the Web front-ends to the service applications.  So from the home page of Central Administration click the Manage service applications link in the Application Management section>

 

16. In the Service Applications page, when you click the <New> button, you'll see a list of Service Applications types to create.  Note that you now see the ones relevant to Office Web Apps.  These are the ones we now have to create.  So, from this dropdown, click the Word Viewing Service option.  The Word Viewing Service Application dialog appears.
 
 

17. In the Word Viewing Service Application dialog you should enter:
      - The Name of the service application
      - Determine if you wish to use an existing application pool, or create a new one.  In this instance, use the existing Default application pool
      - Make sure the checkbox is checked to add this service application's proxy to the farm's default proxy list
      - Click <OK> when complete

 

18. Now that you've created the service application for the Word Viewing Service, you'll need to create one for the PowerPoint Service Application.

 

19. Now, depending on how you originally installed SharePoint 2010, you may or may not have to create a service application for the Excel Services Application.  If you installed via the wizard-based GUI, this will already have been created.  If you used a scripted install (say, via PowerShell), you may not have created one for Excel.  So, if one doesn't yet exist for Excel Services, create one.
20. Once all the service applications have been created, you'll need to activate the Office Web App features on the site collection you want to access them from.  Note that this is a site collection-scoped feature, so, go to your site collection's top-level site, and from its Site Settings page, click the Site collection features link in the Site Collection Administration section



21. Here, you want to activate the Office Web Apps feature first




 22. And then activate the Open Documents in Client Applications by Default feature


23. Now, when you mouse-over an Office Word document, PowerPoint deck, or Excel Spreadsheet you'll see the following options in the dropdown menu



Now, you're able to view and edit Office content within the browser.  Click the images below for examples of the in-browser Excel, PowerPoint, and Word features.
Excel



PowerPoint



Word



Additional Items to Consider
While you can go through the UI to perform the activation of the features on a site collection, when you have multiple site collections going through the UI is not only tedious, but a bit time consuming.  You can create a PowerShell script and use the Enable-SPFeature to activate features via script.  So you could loop through all the site collections in a web application and enable them that way.
Also, when creating the necessary service applications, you can also create specific application pools (along with designated managed accounts) to run these service applications.  Keep in mind that whatever new accounts you use (if not using the default) that they need to have read/write access to the SPConfig and all content databases that house the site collections where Office Web Apps was activated.




Reference:

http://www.mukalian.com/blog/post/2010/12/11/Installing-Office-Web-Apps-Existing-SharePoint-2010-Server-Farm.aspx