Used mac

[Fallenheart]

Question, I have never owned a Mac and just recently bought one used from a yard sale. Am I able to fully wipe the computer? The computer has a password "I don't know it" and I read online about find my mac that could wipe and lock the device. Am I able to redo the computer so find my mac is removed fully and reload the OS so no passwords? I've had iPhone and I know you can't reset the phone and remove password without knowing passwords to account, is the Mac pro tower the same? Or can I just add a new hard drive and reload OS like Windows?

 

[CapnDavey]

If you have a mac os install DVD or flash drive you can do a clean install and start fresh