I want to factory reset my secondhand iPhone 5c?

I want to know because it's secondhand and IIm wondering if it will cause issues. Also, I don't really have any idea how to factory reset in the first place. I don't have a laptop to do it with so I need to know how to maybe use my iPad mini to do it? I really have no clue.

No, it doesn't make a difference if it is secondhand or not.
Check in the Settings > General > Reset > Erase All Content and Settings