If it isn't part of an index, as it is on QSI decoders:
Programming, push, push, push until it reads Ops Mode.
Dial up CV 64, enter a value mid-range for the range of values the manual says that CV can have.
Press Enter.
Press Exit
This assumes a DT400 or similar throttle.
Really, you should get into both manuals, the one for the DCS and the manual for your version of LokSound.