To add a sub to a scorecard, a sub reservation must be made. That can either be done in one of two ways
When you're a league administrator, you can click on "Request Sub" and then click on "Add a Sub Reservation". From there, you can choose the round, the regular player, and the sub who is going to play for that regular player.
Alternatively, a player can make a sub request, at which time the subs will be e-mailed an invitation. The first sub to accept the sub request through the link in the inviation will "reserve" the sub request, and
For a full end-to-end demo of the sub request functionality, click here