You drag them over to the bomb slots, next to the food/potion slots.
Inventory, select bomb, press X, select slot.
In combat, bombs are accesible via L1(where you select signs), select the bomb(you will see it afterwards in the bottom left corner of the screen below you potions/food), press R1 to deploy.
How do I throw a bomb in Witcher 3?
First you have to make sure the bomb slots are filled. Then press L1 to select your bomb. Then press R1 to quick throw the bomb or hold R1 to do a precision throw. Throwing bombs in The Witcher 3 for PS4
How do you use grapeshot bombs Witcher 3?
The Witcher 3: White Orchard, Calcium Equum, Grapeshot Bombs
How do you use bombs in Witcher 3 Xbox one?
Bombs require the collection of materials around the world and to be crafted in the ‘Alchemy’ section of the main menu. You can quick-throw bombs with the tap of a button, or hold it down and the camera will snap behind Geralt for you to aim it.
How do I use samum in Witcher 3?
Alchemy: making a Samum bomb
Inside the cave look up at the ledge and toss your bomb of choice. The Cockatrice will screech and fly off through a different exit. Outside you’ll need to whistle Roach and follow the creature until it’s ready to swoop back and fight you in the open.