Now it's time to wire the NeoPixels to your board. I left about 3cm of wire on the LED's so the holder could rotate around without snagging the wires or leaving loose coils hanging out of the ring.
Solder the LED ground to the Pro Trinket ground. Solder the LED 5V pad to the Bat+ connection. Remember that you're soldering these to the flat side of the Pro Trinket, so everything's going to be soldered with the board upside-down. You're also connecting these wires to the pins you trimmed off from the Power Backpack. It's not going to be a bulletproof connection, but since these components aren't going to be moving around inside the ring the wires fatiguing and snapping shouldn't be a problem.
The LED data line (black wire) goes to Pin 0 on the Trinket. It's labeled RX on the board. This one's just a standard through hole soldering job so it should be no problem.
If you're confused, this diagram should help.