Moving the CG back means move it towards the tail. Adding tail weight is one way. Moving the battery pack or removing weight (if possible) from the nose is better.

Oh, on some planes, you can adjust the CG by just moving the wing slightly. Moving the wing forward has the effect of moving the CG back.

Even though it moves forward on the fuse when you slide the wing forward, it's still moving the CG "back" since it's the location of the CG on the wing that you care about, where it is on the fuse doesn't matter. (slightly over simplified, but close enough)