First: Welcome to the Bolt! Second: Buy a shop manual available fro m sellers Jim Carter, etc. Third: Take it slow. Fourth: Be safe. Lecture over.
Under the cab you should see a drain petcock extending through the floor that is attached to the fuel line running forward to the fuel pump. Disconnet the line(hopefully it still has the short flex line) at the petcock, use a catch pan and open the petcock to drain any old fuel out. You can somewhat, but not thoroughly, clean the tank by pouring fresh fuel into the tank, say a gallon, and drain out rust particulates that way. It is even better if you remove the petcock for the clean fuel draining. A ore thorough cleaning can be done with the tank removed obviously. But, the point is to first get the engine running isn't it? I would buy a new battery. Good Luck.

Drew