If you haven't yet read our general help article on the gear you need to play and/or sing on JamKazam, we recommend you read that article now and then come back to this one.
If you want to both sing and play and instrument in JamKazam sessions, we'd recommend you return to the gear requirements by instrument help article index and choose your instrument from that list. Those help articles explain both how to make your instrument work with JamKazam and how to sing in JamKazam while playing.
For vocalists, the simple setup in the diagram below will work well for singing on JamKazam.
In this configuration, you need an audio interface for your Mac computer or for your Windows computer, a microphone, a microphone stand, an XLR cable, and a pair of headphones.
Connect the microphone using the XLR cable to one of the audio input ports on your audio interface. Mount the microphone on the mic stand so that it's held in place. And then connect your headphones into the headphone port on the audio interface. That's about it. You'll want to position the microphone on the stand so that the mic is at a comfortable height and position relative to your mouth, of course.
If you want to sing along with some kind of accompaniment or backing track recording, you can accomplish this quite easily in JamKazam, by either: (a) connecting an audio source to the second audio input port on your audio interface and playing whatever music you want into and through that second audio input; or (b) using the backing track feature in the JamKazam app to open audio files you have saved on your computer and playing those within your session using the JamKazam app.