1Get the assembled board
Source&assemble it yourself or buy some from me
2Flash the firmware with your UUID into the ATTiny
There's a default-pinout 2x3 socket for ISP on the board. Just plug a USB-ISP in according to the pinout and you're good to go!
3Connect the board inside the device in question
If there's 5V inside the device, connect it directly. If there's only 220V, add a sufficiently trustworthy 5V PSU as described in "details". Either way, make sure that the antenna of the NRF module can actually transmit - i.e. you're not putting it inside a fully-metal case.
4Turn it on and test if the packets are received at the base station
5Test whether the device sends the "shutting down" packet
If it doesn't, make the storage capacitor larger until it does. Suitable storage capacitors can be sourced from PC motherboards - they're low-voltage and high-capacity, just like expected here. If the "shutting down" thing fails, the device will still work - just that the power cut-off will not be detected instantly.