In the menu bar on the left side of the screen, select the "settings" option.

Within settings select "sessions".

On the new screen, from the list of sessions select the session you want to delete players from.

Select the "session players" tab.

Find the player/s you want to delete and press the blue (bin) button on the right side of the player's information.

A warning message will show up indicating that you are about to delete the selected player from the session.

Press "Ok".