Gear shift frozen

[frsher]

Hello and thanks for the help in advance. I have a next to new Schwin 5 speed cruser (2 years old) given to me. I have arthritis and this bike is the most comfortable one I have tried, so when it stopped working I was not a happy camper. Someone tried to help me get it out of storage and managed to take the chain off. I know nothing about fixing bikes beyond the obvious (like a flat tire). He "fixed" it but now the gears shift on the handle will not move. Not a lick. I don't want to force it in case I do further damage but have no idea where to begin to look to find a problem. Now, could it be as simple as oiling something? I am loath to take it to a shop, the last bike I had came back in worse shape than it went it. Because it wasn't worth fixing so the clerk said.
I don't mind trying to figure it out using the repair guides here but where do I start?

[Jordan300]

Do you by chance have a picture of it? Does the bike ride ok and that it just does not shift? I have had someone having trouble with brakes and gears before and it turned out the handlebars had just been twisted around the head tube one too many times. If not it could just need some TLC.

[frsher]

Actually before all this happened with the chain, the bike road beautifully. It sometimes felt like I was riging through mud but I chalked that up to it being new and unfamiliar. I am going to try to send a picture.