Wiping and reformatting MacBook Air

Have a work computer that we can pretty much do what we want with. They said they won't work on them anymore but aren't going to ask for them back. It's gotten to the point where it says my OS is out of date, my browsers are out of date but won't update bc of my OS. I can't open important websites (bank, credit card, etc) because everything is so out of date.

Looking for someone to wipe it clean of everything, anything related to work, etc. Reinstall OS and Office. Any takers?