Hello ynnad026,

Here are the official Backgammon rules on FlyOrDie:

https://www.flyordie.com/backgammon/rules

If you scroll down, you’ll also find the explanation of the scoring.
You can access the rules directly from the game's start page as well:

On a computer, by clicking the question mark icon next to the Play button.

On a smartphone or tablet, by tapping the blue arrow below the Play button.

If you’re interested in how the scoring and rating calculations work, take a look at FlyOrDie’s general rating table, which applies to all games:

https://www.flyordie.com/games/help/rating_system.html