Ok, this might be obvious for those of us with experience, but maybe not for a first timer (by no means calling first timer 'stupid' or insulting in any way- we all started as newbs).
You are pulling up on the outer snap ring before you try removing it? I find it a little easier if you rotate them around to ensure they didn't have any residue or anything that could cause them to stick, then pull em off.
Grab a long handle wrench or pliers, and use the keg handle as leverage- you can do this by yourself but might be easier with a third hand so you can steady the tool as you pull up wring and smack the handle a little.