If you are a total newbie, try this guide:
Here are some good write-ups to show how to effectively use AFL++:
If you do not want to follow a tutorial but rather try an exercise type of training, then we can highly recommend the following:
Here is good workflow description for frida_mode:
If you are interested in fuzzing structured data (where you define what the structure is), these links have you covered (some are outdated though):
If you find other good ones, please send them to us :-)