Start out in Adventure mode. Click each formation when you encounter it for the first time. Use the arrow buttons in the menu for easy navigation, or double-click to mark any section or area as the active one. You can also expand and collapse sections and areas as needed without changing which one is "active".
When you visit the Veldt, switch to Veldt mode. All of the packs that you will encounter are listed here. When you get into a fight, select the appropriate formation, and record the outcome -- Gau used Leap, Gau returned to the party, or neither. The tool will record any rages you learned as a result, and advance to the next pack automatically. If the tool loses track of which pack you're on (e.g. if you save and load your game), you can use ctrl-F to find your place.
Use the Rages list to see the list of all rages. Click a rage to toggle its status; in case you've started using the tool in the middle of a game, you can quickly record which Rages Gau already knows.
Don't forget to Save. Recommendation: Click the Save button in the menu only when you save your game. This way, if you are forced to reset your game, you can simply reload the web page and the tool will still be in sync with your game.