You can learn Fusion with the standalone Fusion Studio or inside DaVinci Resolve. When learning from tutorials you can follow both as well.
Loading a *.comp file from Fusion Studio into the Resolve Fusion tab is straight forward:
- Create an empty Fusion clip in the timeline and go to the Fusion tab.
- Go to the menu File -> Import Fusion Composition.
- Put any external media into the Media Pool. Then check all the loader and saver nodes and replace them with MediaIn/MediaOut nodes.
Watch this tutorial for the demonstration and a few hints of what to watch out for.