I'll provide a wiki link to the article on that sheet. The help desk has one also, but doesn't (as far as I can tell) have links to sub sections yet. <a href="https://wiki.roll20.net/Pathfinder_Official" rel="nofollow">https://wiki.roll20.net/Pathfinder_Official</a> If you click on the 2.5.7 Weapon Attacks link in the table of contents, it will take you to an image of an attack as shown after clicking the cog. Notice the critical range blank right under the checkbox for rolling the attack. In the example, it is a 19. You enter the lowest number you can crit on. Every d20 roll that number or above will be treated as a critical threat.