How do I connect a Juno LED light to a switch when the light receives power first?
Harper's comment is, as usual, a correct summary of the solution. Here (copied from part of another question) is the full diagram:



Light fixture junction box:


All whites (neutral) together
All grounds (green or bare) together
Blacks from 2-wire &amp; 3-wire cable together (hot)
Mark light fixture black wire (may be labeled "hot" or "switched hot", but it should be the only wire or screw other than white/neutral and ground) with red tape.
Reds from light fixture and 3-wire cable together (switched hot)


Switch junction box:


All grounds (green or bare) together
Black to "hot" screw on switch
Red to "switched hot" screw on switch


If switch does NOT use neutral:


Cap white (neutral) with a wire nut


Note that with a simple (not smart, not dimmable, not timer, etc.) switch there is no functional difference between the hot &amp; switched-hot connections, but if there is a clear indication on the switch (or in the switch instructions), follow the directions.

If switch USES neutral (e.g., smart switch)


White to neutral screw on switch.