Add a practice match to the match log
Say
"Scroll down to the Match Log. This is where you record every match you play. Let's add a fake one together so you know how it works. Set the Week to 1 — that means trial, it does not count in the standings. The Match number should already say 1. For Opponent, type 'Practice.' For Score, type '2-1'. For W/L, pick W. For Notes, type anything — 'first test run' is fine. Now click '+ Add row.'"
Do
Walk them through it live on your projected screen. After clicking Add row, point out: the row appears in the table above, the match number auto-incremented to 2, and the Week 1 row is dimmed because it is a trial.
Say
"See how that row is faded? That is because Week 1 matches are practice. They do not show up on the leaderboard. Starting Week 2, your matches count."