Your right lever should operate the rear derailleur - pull it towards you to go to an easier gear (bigger freewheel cog), push it away to go to a harder gear (smaller freewheel cog).
If you have a front derailleur, it'll be on the left side and operate in reverse - away from you will bring you to a smaller chainring (easier gear) while towards you will bring you to a larger chainring (harder gear).
If you have access to a stand or a way to elevate the rear wheel, it wouldn't hurt to practice a bit while off the bike, so you can see just how it operates - if you've got frictions shifters, which I assume you do, the shifting will depend on you to find the gear. If you shift and the chain continues to make noise, you'll need to move the lever slightly to get the derailleur more in line with the freewheel cog.
I hope this helps.