MLS - Offering Players

I've started a game playing in MLS. I think I have a basic understanding of the squad/roster rules but how do you offer players to other MLS teams?

The only way I can do it is for a 'designated player' allocation. Is there anyway way to offer in exchange for a 'foreign', 'develeopment player' or draft pick?

Any help much appreciated - would like to add more another foreign player space to my side but unsure how to.

Thanks!

I don't think you can or else I couldn't find how when I played as Toronto.