Hi @loric - Thanks for reaching out!
While it is hard to say for certain without seeing your bag in person, a silicone seam sealant will usually work well to apply those patches. You can spread the sealant thinly over the back of the patch, press it firmly onto the pack in the desired location, then leave it overnight with something heavy holding it down. With multiple patches you may have to do this over a few days, but you should be good to go!
Hopefully this helps!