If you are new to backgammon you should do the following before starting play:

1 - Turn off the Cube. First item in the Options menu,
2 - Put Skill Level on Novice. First item in the Skill menu

Read these documents included in the same folder as the game:

Basic Backgammon Rules explains the rules of the game. David's Backgammon enforces the rules.

Backgammon Glossary explains some of the special words used in backgammon.