Yeah, we need more documentation on some of the actions and objects we have built in...
Basically, the "join group" action should be used with the "group" object. You create the object and set it up on your groups. Then, you associate the join group action with that object.
The same goes for the "album image upload" action that goes with the "photo album" object group.
The profile object doesn't have any actions defined for it. However, with JFBConnect, you can create your own actions. So, for instance, if you wanted a "poke" or "like" or even a "disagree" button that you wanted to place on the user's profile, you could do that. Then, when a visitor views the page, they can see and click that button and it would show in their Timeline as something like "John disagrees with Alex".
So, our defined actions are for things that a user can already 'do' with JomSocial: join, upload, attend an event (coming soon). You can then build your own actions as well with the Open Graph - Custom plugin for 'button' type actions.
Hope that makes sense, but if not, let us know.
Thanks,
Alex