Direct quote from https://www.commonapp.org/application/instructions.aspx

(Common) Application Versions
"The Common Application should generally be completed once, with identical copies sent to all colleges. You should create a new version if you wish to correct an error discovered after submission or provide new information not available when you first submitted the application. It is not necessary to "customize" your Common Application for individual colleges. Individual college supplements and supplemental essay questions should be used to provide special information to different colleges. Below are the steps necessary to create an alternate version.

Step1: You must submit the Common Application to at least one institution first. You cannot create an alternate version until this has occurred.

Step 2: You must log out of the application then go to this special URL:
https://www.commonapp.org/CommonApp/Default.aspx?allowcopy=true

and login using your existing User Name and Password.

Step 3: Upon login you will be taken to the 'Common Application' page, where you will see information about the application you have already submitted. The ability to create an alternate version of your submitted Common Application is now activated, and you should click on the ‘Replicate’ link to make an alternate version of your submitted application. When this is complete, a second version will be visible on your screen and a special drop down list will appear in the upper right corner of your application. You can use this drop down to move between application versions.

All data from your original version of your Common Application will be transferred to your alternate version, with the exception of any documents that you uploaded. You may edit any of this information before you submit it to another institution.

You only need to go to the special URL the first time you create an alternative version. Thereafter, additional application versions can be made by going to the ‘Common Application’ section within your original Common Application and using the ‘Replicate’ link. You may make up to 10 versions, including the original version. You only need your original User Name and Password to access all versions.

When you create the first alternate version of your application you will see a simple confirmation message. If you create any additional alternate versions of your application you will need to complete two affirmation statements then click the 'OK' button. You may also click the 'Cancel' button to not create the new alternate version.

You will have a separate My Colleges page for each application version. Each institution can only be on the My Colleges list of one application version, and you can have a total of 20 institutions across all versions.

You can move an institution from one version to a different version at any time prior to submitting the Common App to that institution by selecting the college on the My Colleges page and clicking on the "Move College" button. "