Hi Tel
Like G.H. says, the best way to learn is to get in the manual and just play with the machine - but here's a couple of starters.
1. Go to Chapter 3.3 (Copy) [I'm now assuming that you haven't created any patterns or saved any patterns into the user section - if you have, press the preset/user to have the sr-16 list the user patterns and see what user pattern is empty - this is your destination] hit the preset/user button again to go to preset pattern list. Pick a preset pattern you like - maybe a good beat, but you want a different drum kit, or maybe you like everything but the snare. Once you find a preset pattern you like, press and keep holding the copy button (chapter 3.3.) then using either the number keys to type in the empty user pattern #, or the up and down buttons right above the fill button, select the empty user pattern # where you want to put the copy. (You're still holding down the copy button, remember?) now press play - the display should say copy done. release both buttons.
Now that you have a user copy, if you want to change the drum kit, hit the drum kit button, and hit the up and down buttons to find one you like. Say you like the kit, but the snare is too loud. Hit the drumset button so the screen says drumset select. Then hit the tempo up button. You will see one of the drums, cymbals, or whatever that is in that kit. Hit the snare pad and the display will list the name of the snare drum in that kit. Hit the tempo up button again and it will show the volume for the snare, which you can change with the up and down buttons. I you keep hitting the tempo up button it will list several different parameters for that snare drum, the last will ask if you want to save the set to the pattern number you copied the original preset pattern to (chapter 4.8).
You really want to read up on chaters 2, 3, and 4 and play with the sr16 while you read them. Once you create a few patterns and edit some drum kits, it will come easier.
Have fun
mutt