I can't find any options for controls or how to access the settings.

This button has a hard-coded position. Sometimes another mod will add a button in the same location, and you will not be able to see it.

Thanks!
Also, what version of the fabric API does this require?

It should work with all versions of fabric-api for the relevant Minecraft version. I have confirmed that it works with fabric-api 0.25.1 build 416.