To get the best quality recording, we strongly recommend using headphones, to avoid the output sound of the device being captured back through the mic. Simple earplugs are sufficient.
The first step is then to customize the different instruments you want to use, by adjusting their level to each other, possibly add effect through the FX pane.
Once you are happy with the mix, you need to adjust the mic level versus the music one, through the Recording Volumes pane.
After that, you are ready to go. Click on the REC button of the top bar, start the accompanying instruments and start singing/playing. When you are finished, stop the instruments, then click on the STOP button on the top bar. A new audio file will then be created in your user's Music folder for you to enjoy and share.
You may need a few trials before you get the perfect mix, but after that you won't need to adjust anything anymore.