How to make MOH point to CUSTOM-MOH Catagory?

I have two D40 phones with two lines each runing on AsteriskNOW 11.16.0. I am trying to configure, through the GUI interface, MOH to use my *.wav file in CUSTOM-MOH category and play only CUSTOM-MOH when put on hold . I have not found the way to do this short of deleting the “default” category and hoping category CUSTOM-MOH will play. Any guidance on configuration of MOH to point to CUSTOM-MOH category would be appreciated.