Pick songs that you like, suit your style and you are capable of singing and playing.
When you pick a song beyond your capabilities you will know it doesn’t sound good and therefore your motivation to perform it will dissipate
For beginning singers start with a song that is already in a key you can sing a long with for practicing. Eventually you will learn how to transpose and it won’t matter what key it is in but for now make things easier to learn and don’t chose something you can’t sing along with.
Pick a singer that you really like and imitate her or him for the sake of learning the style. Eventually you will develop your own style and people will want to sound like you but for now this is a method to use to learn songs and discover what works for your voice and what doesn’t.
Perform the songs you learn to whom ever will listen and do it as often as you can. Keep track of your songs, the keys you sing them in and have either the sheet music or the lyrics with the chords above them and build up a repertoire.
Have a goal in mind like I will learn this song this week and perform it for someone this weekend!
Have fun!
Gayle