I have a ''99 Saturn SC2 and recently it was making a squeaking noise which I found out was the belt, I replaced the belt because it was really loose, now I think the tensioner is the problem and I don''t know if it is broken and need a new one or it just needs to be tightened. Does anyone know the best way to fix this or had a similar problem?

You cant tighten the tensioner. If the spring inside is broken or worn, replace the tensioner.