Assuming you want to use the Hero_FPP and the First Person template code, then yes. You can export the Hero_FPP skeleton to FBX and then rig your arms to it. When you import your arms back in, select the existing Hero_FPP skeleton in the import dialog. Then, in the Hero blueprint, just swap out the existing mesh for your new one. If you’ve changed the proportions at all, you may need to retarget, but otherwise, everything should Just Work™.
Edit: also, those are really nice arms.