Soldering WS2812B Daisy-Chain
Notice that the top picture shows just the LEDs, but the bottom picture shows little circuit boards (the LEDs are attached on the other side, not shown).
If you just have the LEDs (not attached to the little circuit boards), then you have four pins. GND, 5V, data in, data out. No problem.
The circuit boards have two 5V pads and two GND pads for easy daisy-chaining, but they're wired together on the circuit board. It doesn't matter which one you connect. You can connect both if you want to (e.g. for mechanical stability) but you don't have to.