First, you will need to know what citation style to use. Check your assignment or syllabus, or ask your professor if you are not sure. KnightCite and BibMe are two resources available for free online that will create a citation from the information you provide. You still need to double-check what they give you; a citation generator uses what you input, so watch out for typing errors.
Most databases provide citations for you, so look around for a link that says "Cite" or "Citation Tools." Be sure to check the result against your style manual!
If you need additional help with writing or citation, contact the GTC Writing Center of the campus closest to you.