Login to your club control panel. Click Teams from the left-hand menu and then click Training.
Navigate to a specific training session.
Underneath Attendance, click into a specific player that is listed.
A pop-up window should then appear on the right-hand side. Click the toggle option next to 'Excused from attending'.
A toggle in green marks the player as excused. Click Save towards the bottom-right of the screen for this change to come into effect.