For a Percentile, you will roll 2 dice: The "d10 (Percentile)" first, and the "d10" second (you can change how many different dice you are rolling by clicking the small + sign next to the Dice rolls box). It's pretty obvious what you get when the roll is resolved, but there are a couple of tricky situations, and I'll go over them below.
The only way to roll a true 100% is to roll all "0" on both dice.
If the Percentile dice rolls "00" it counts as "0," so your roll on the standard d10 will be your percentage.
If the Percentile dice rolls "10," and the standard d10 rolls "0," then your percentage is 10%. If the standard d10 rolls anything OTHER than "0," then your percentage will be 10 + whatever number is rolled on your standard d10.
If you have any questions or issues, let me know. Also, there will be a quick reference chart coming soon!
AMdG