Did you follow this documentation?
This might also help to read, they reference the grbl setup also.
You need to cruise through these documents and it will help you learn how to drive your laser and what’s important to know.
You can skip section you don’t care about, but you will be aware of them.
There is documentation on setting your ‘cut/layer’ which is where the power speed are located.
There are also plenty of videos on using Lightburn as a beginner I’d suggest you watch a couple of them …
Good luck
