If you want to use the Vykes Dragonbolt, you'll need to have a seal. This is because the Dragonbolt requires a specific type of energy in order to function - something that can only be provided by a seal. Once you have the seal, simply place it on the ground and stand within its radius to charge up the Dragonbolt. Doing so will allow you to fire off a powerful blast that should take down most enemies with ease. Just make sure you're prepared for the recoil!