You succeed on a passive check the same way as with normal checks, if your result is equal or higher than the checks' DC.
Specifically, the rules which define passive checks (PHB p. 176) don't specify how success or failure works because they are the same. Or, the success/failure condition is the same, because the rules don't change them.
Either way, you succeed on a passive ability check if your result is equal or higher than the DC you are making it against. The only difference is that instead of your result being the result of a d20 roll plus your modifier, it equals your static score (which is 10 + said modifier).
Obviously replace DC with the appropriate check result if you are using it in a contest, such as a creatures Dexterity (Stealth) check against other creatures passive Wisdom (Perception) checks when hiding.