@CaliaMoko Wow - this really takes me back to my days when I worked as a guitar tutor
This is a crucial aspect of playing and is something worth taking your time with to get right
I would suggest doing some research on “PIMA”
PIMA is an acronym that guides you as to which right hand finger to use to pluck each note in a piece
After a while this simple becomes “second nature” but following this principle on a couple of simple pieces will give you a strong foundation and set you off in the right direction
You should be able to find some simple tabs (and in this day an age there are probably a gazillion videos on YouTube) on how to apply PIMA and even find some notation/tab with PIMA above the notation
My final bit of advice (which applies to learning ALL new techniques) is that:
“practice doesn’t make perfect - practice makes permanent”ALWAYS practice playing at the speed you can play the HARDEST part. This often means playing the simple parts painfully slowly
This is really important otherwise you could fall in to the trap of developing an inconsistent timing - eg playing the easy bits quickly and then slowing down for the hard bits
It is VERY easy for this inconsistency to become “baked in” to your playing, which is something you don’t want
Do some research on PIMA and have some fun!