Try searching the forum using keywords "removing shift knob" and you should find a few threads to read about the process. Any process for removing the knob on a 2007-2016 Acadia would be appropriate.

 

Generally, just do a steady firm upward pull while twisting back and forth on the handle slightly. There are also some Youtube videos about it.
Here is part of one that show how on a newer Acadia, but 2013 is pretty much the same.