Hi Lloyd,
Sorry forgot to check if you're actually altering 0nboard factory styles ( I never do, I usually do a copy and alter those) hence I never remember to ask.

Anyway if you're altering factory styles, you have to unprotect them.
GlobalMode
Preferences
Remove Factory Protect ( UN hi light the blue square)


Choose style
Press on Drum Track
Menu button
Choose Track Controls
Drum edit Tab
Hi light Bass Drum ( or whatever)
Press play ( start/stop) so you can hear track playing
To make sure it's working, I turned bass volume up and down so I know it is working.
Then changed some of the other settings.
If it's playing you can hear changes in realtime as you're doing them.
When finished
Dropdown menu and write.
Not sure what the different ones do, but I really only want to save mine for this particular style, so I've done it as current style settings.