Cleaning up my Hard Drive

Was thinking of reformatting one of my hard drive but I am finding it hard to erase the files that was in it. Now I am on google to search on how to erase hard drive. I need to learn it as I don't know who will do it for me. My brother is not here and I badly need to clean my hard drive. Ok off to search for the steps on how to clean my hard drive. Bye for now!