There is nothing extra to fill in: vote on any upcoming match in its “Predictions” panel while logged in, and that vote becomes a prediction. A correct call pays by how hard it was — a 50/50 pick is worth 1 point, backing a side everyone doubted pays more (40% → 1.25, 25% → 2, capped at 5), and calling the obvious favourite pays less. Votes cast after kickoff still count for the crowd percentages, but score nothing.