How do activity imports work?

I apologize if this has been covered elsewhere, but I have not been able to find an answer. I have been trying to import activities in the form of TCX files (exported from HealthSync or Google Fit) into Kailona. When I click import, I am given 3 options: Activity, Documents, FHIR. Choosing documents puts the file in the documents folder. Choosing either of the others does not seem to do anything.

Can someone help me figure out what I am doing wrong?