1. Go to MyCAREER
2. Choose MyPLAYER Appearance
3. Select Jump Shot Creator
4. Hit the Y button to Edit/Save
5. Select Create A Jump Shot and enter at least 4 characters and save it and achievement will pop.
Edit: You can only do this once you are past the high school and college portions of MyCAREER. Once you are able to access the Neighborhood, you can create a jump shot.