Sign in and click on the HQ Home icon at the top of your screen.
Once in "SportsEngine HQ," click on the Competition tab, then choose Rostering.
Under Rostering, click the Transfer People sub-tab.
Choose the club/league to transfer players within.
Select the team you want to transfer a player from (left) and select the team you want to transfer that player to (right).
Click, drag, and drop that player from the left to their new team on the right.
NOTE: The player will be inactive on the initial roster you transferred the player from.