First, create an Enrollment Field:
1. Go to Programs > Configurations > Enrollment Fields.
2. Click Add Enrollment Field.
3. Input the desired data for the new Enrollment Field.
4. Click Add.

Then, add Enrollment Field to the Program:
1. Go to Programs > Manage Programs and select desired program.
2. Click on the 2 Configuration tab and scroll down to Enrollment Fields.
3. Click Add Enrollment Field.
4. Input desired data.
5. Click Add. 

Here is a video to watch on how to add an Enrollment Field - https://iframe.mediadelivery.net/play/165597/2ffd054a-54c3-468a-9f46-34043a6b63d3