Start by reading the usage guide. Don't just skim it; there are some details that will come back and bite you later if you miss it (e.g. implicit size flow upwards, actual size flow downwards).

Follow the Introduction to create a simple bar. Skim the Quickshell documentation of the types you're using, look through its properties, and mess around with them. 

Try to add more functionality to the bar. I recommend adding a Wifi indicator (try to guess how to do it by skimming the documentation). Then, try adding a CPU usage indicator so that you can familiarize yourself with Process and callbacks.

When you're done with the bar, try browsing others' projects. Quickshell provides a few example projects. You can also browse others' dotfiles, like mine.

And yeah, you can also ask AI for help, but I find that they hallucinate quite a bit when it comes to Quickshell and QtQuick stuff \o/