As GM, you can use modifiers for any rolls made by you or the player(s). Given how this game tends to play out, you might find that the player(s) actually begin negotiating with you for modifiers to their rolls, so it’ll add an ongoing bargain to your conversations, and also to the narrative flow of whatever’s happening. When might you apply them?...
In fights
During fights, each combatant will have a ‘to hit’ modifier automatically in their stats. So if a brawler swings their longblade at a creature wearing leathers, they’ll add +2 to their d6 attack roll. If they’re successful (in other words 4 or over in total), the d6 damage will have a +4 modifier for the longblade, and a -2 for the leathers. You can adjust any of those modifiers though, like if the weapon or armour is damaged, or if the circumstances suggest it. So it’ll be more difficult to hit a creature if the ground’s giving way or in the midst of a blazing storm, or easier if the creature’s lying prone on the ground.
In all other cases
Beyond any specific modifiers in the game though, like if a character decides to dodge & parry, you can add or subtract modifiers simply if something feels more or less difficult to achieve in the moment. Encourage the player(s) to bargain with you on that front. For example, if a character’s trying to charm their way into a tavern but the bouncer’s tough to crack, you might suggest it’ll be a +1 to a presence traits roll, but the player might remind you that their character had slipped the bouncer a bribe, and ask if that adds a -1 to cancel that out. If it feels right & fair in the moment, go for it, and always look to explain quickly why you’re applying any modifiers.
what's next?
Ok, so from here you might want to...
...move onto how to churn rumours in the game
...return to the rules of the chaos intro
...or dive into the character creation rules
Remember, though, that you can navigate anywhere on the site using the menus on each page, and if you ever get lost, roll 1d6 and we'll see what perils you encounter!