Fulcro has a number of resources that can get you going.
The Developer’s Tutorial is an interactive guide to the basics.
You can also read it online.
The Developer’s Guide covers the entire library, and also has a Getting Started chapter that is great for beginners.
There is a playlist of videos for different topics. This playlist is expanding, so check back often:
I’ve given a few talks on Untangled, which was the root project of Fulcro. The names are out of date, but the concepts are still the same. Use the playlist control at the top-left of the video to choose what you want to watch.
Most functions have good doc strings that explain the purpose of the function. Use your IDE’s help to see these documentation elements.