Ok so with lesser known older songs its hard to find backing tracks. Also the track quality differs greatly from track to track depending on these things.
I tried to find Nehnanana by Vaya con dios and i couldnt find it.

So if this is the song you wanted to do. Has the same name...

This is the link:

Use the link and place it in: https://y2mate.com/

Click download audio... Dont download the video. You dont need it.

Then what i do is use Audacity to connect to my mic. Record audio, and i film myself from my phone singing into the mic, 1 take per openmic rules. Master it a bit if you know how to... ( i suck at it haha)... I just amplify the quieter parts.

Then i use Filmora and sync the audio i got from the phone and mic recording.
Ita quite easy. Do some simple color correction and render.
Thats that really. You can make a thumbnail if you want but thats just for show.