How am I able to change my base location?

Raise a travel request from GESS and get the required approvals

I am facing the same problem, I have even completed the training but still my manager don't agree to give me transfer. It completely depends on your manager.

Either you should be having a strong genuine reason like major health issue with you or your parent, planning to get married,..etc or you should get a project that has an ODC in the location that you are looking to get transferred.I feel the latter is best and easiest way to get location transfer.