O.K. it cranks. If the motor is turning like normal but not firing then you have a spark or a fuel issue.
If it is turning over slower than normal try a jump start and then if you have the original battery, get a new one. if your battery is new drive around for at least a half hour or so, if the problem persists then you should talk to who ever you bought the battery from and have it checked for holding a charge.
If your gas tank is empty it could be vapor lock from the cold. Try adding a can of dry gas (get it at an auto parts store, its cheap)
Other issues will need a mechanic since your question presupposes that you are not particularly mechanical.
Good news is that any of the possible problems should be pretty cheap i.e., no more than $100.00 at any decent shop.
Good luck