The 2-pin JST cable from the battery connects directly into battery port on the PowerBoost 1000C. Voltage and Ground wires from the PowerBoost 1000C connect to the 3-pin JST port on the PyPortal (doesn't matter which one).
Use a 2-wire cable (6cm long) to connect the toggle switch to the PowerBoost. Remove a bit of insulation from the tips of the wire and tin them with a bit of solder. Connect the wires to the middle pin and either the far left or right pin on the switch. A third helping hand tool can hold the switch and wire in place while soldering.
Solder the two wires from the switch to the EN and GND pins on the PowerBoost. We'll use the 3-pin JST cable soon. Polarity doesn't matter so the wires can go either way.
We'll use a 3-pin JST cable (9cm long) to easily connect the PowerBoost to the PyPortal. We only need two of the three wires, so you can remove the white wire. Using wire strippers, remove a bit of insulation from the tips of the wire and tin them with a bit of solder. Solder the wires to the voltage (+) and ground (–) pins on the USB output of the PowerBoost.
Plug in the 2-pin JST cable from the lipo battery into the battery port on the PowerBoost. Then, connect the 3-pin JST from the PowerBoost to either of the two 3-pin ports on the PyPortal. Use the toggle switch to turn the circuit on and off.
You can easily disconnect the battery from the PowerBoost, and disconnect the PowerBoost from the PyPortal. This makes it easy to install in and out of project enclosures, stands and the like. You could even wire the toggle switch to a 2-pin JST cable set for extra modularity.