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Although we don’t have any tutorials for dodge and burn, there are many on YouTube. Even though most are for Photoshop, the effect is the same. Basically burn darkens the image where you paint on (think of burning toast), and dodge lightens it. You can find some quick tutorials here:
For the Pro Editor tools, there are a lot of tutorials on YouTube:
https://www.youtube.com/results?search_query=pixlr+tutorial (or you can search for the particular tool you need help with)
Let us know if you have any other questions!