This is about describing how you are using those advantages (or threats) in combat. In order to help your players come up with ideas of how they're giving or using those boost or setback dice, it may be handy to come up with some features for a particular scene. Things that players can use to describe how they're imparting those dice. For instance, a scene could take place in a warehouse, and it could have features like crates , labour robots , and a mobile crane . Now in the scene, when a player rolls enough advantage he can say he is using a labour robot as a shield, inflicting either a setback die or upgrading the difficulty of an opponent's check. Or maybe he says he is taking an extra maneuver and uses the mobile crane to carry him away from an opponent who is about to attack him. Or maybe his shot broke open a crate and spilling its contents and distracting his target, giving himself or someone else a boost die.
Anyways, not everyone who plays (both players and GM) is going to have the imagination to use those advantages and such, so it may be helpful to have features like this to help the process.