Finding and adding to a list

[8910billiards]

I am stuck!!

I have a Data Type Tournaments. I am trying to add Users to a list inside Tournaments of Players who have signed up to play.

I am stuck on how to search for Players and then ADD them to that list.

Hope this is enough details to figure out what I am trying to do.

Thanks

Scott

[eftomi]

If users authenticate, you can get current user within the expression builder in some action, e.g. in button press workflow.