My Passport (not wireless!) - Please help!

Please help! I’m not a techie AT ALL, hence my problem.

A neighbor “installed” My Passport - the kind that is connected to my PC with an USB - several years ago. I didn’t know what an external hard drive is - not a techie, remember? - and just assumed that if/when the thing was filled, it would communicate that to me. Not so, as I found out the hard way.

I needed to find a current financial document that I’d just completed, and discovered that it had been accidently, permanently deleted. Of course, the first thing I did was to see if My Passport had it, and that’s when I found out that 2017 the latest backup on My Passport.

I’ll have to try and reconstruct the lost document but, in the meantime, I’d like to get My Passport working again. I have no idea how to delete the old files that are on My Passport. I’m under the impression that once there’s room on My Passport, it should begin to back up again?

Can someone give me directions how to do this so that My Passport will work to backup my current documents?

Many Thanks!!