How tf so you record a cover

I’ve been trying to record myself while playing bass to post on insta but my sound quality is awful im putting dig on my school tablet and I’m recording with my phone as I’m playing the song but I can’t hear shit while I’m playing when I listened to my video it didn’t sound good i genuinely don’t know how to record should I play the song and when im editing I just put that song over my playing, If so how do you do that? (Sorry if my sentences don’t make any sense)