Tying in a flood light to existing circuit?

Hello all, I’m planning to add a flood light to my shed that has existing electricity. It has its own breaker box in which one line runs from the breaker to an overhead light, switch, and outlet.

The line first runs over the door to the mentioned spots, I’d like to splice the flood light into that line running over the door. I have a wet condition junction box to tie in the light then out to the other spots.

Is this sound? Will I fry myself or the shed?