You can use the “Get Actor Forward Vector” (or something like this). This will give you the normalized (length = 1) vector of the direction the camera (or the actor) is facing at. Multiplying this vector by e.g. 5 and adding it to the current location will move your camera forward. The same node exists for left/right and up/down. If it’s only exist for right and you want to use it for right, multiply it by -1 or simply multiply it by the axis of the Input Event. Hope that does the trick for u 
Example in pseudo code:
InputHorizontalEvent(float axis)
Actor.AddRelativeLocation(Actor.GetActorRightVector * axis)