Navigate to members->players/parents->statistics & evaluations->enter statistics. You will see the form below:

 First, you will only see choose a level, but the other options will appear as you make your selections. Once you have made your selections, you will a table for each stat group that you selected, displaying stats for all the players who played in the game.

You can enter a stat by typing a value into the input field. When you are done entering stats, you can save statistics.