I recomment a very simple basic exercise first before you even attempt to learn any songs if you are new to slapping.
Slap your open E and pop the fretted E on the D string. Repeat it until you know whether its your middle or index finger is more comfy with slapping.
Pls do this to a metronome.
Proceed until you are comfy to move up the fretboard i.e.
Low E (Slap) E (pop), Low G (Slap) G (Pop), Low A (Slap) A (pop). and so forth.
If you are okay with both the movements of your right and left hands and plus you are sure your slap tone is right, then move on to learning songs... Basics very important at this stage.