Welcome to the community, nice to have you here... That talk about not having a good voice, definitely not true.
Acapella is the word you're looking for in your title, not "Voice Over", and while it's cool, using an instrumental will make it even better even if it's just playing from another phone or a laptop in the background... You also want to make sure the length of your video "from when you start singing" is up to 2 minutes at least.
Lastly you'll need to be adding a link to another video you posted on social media like IG/Twitter called a promotional video... I'm sure one of our judges might drop by to explain these things better, but if you have any questions just reply with them and I'll be sure to respond
RE: Vibes Web 3 music competition week 38 || "Be lifted by MOGmusic" - Voice cover