The neoFlo looks like this and will be on the end of your radiator.
First of all, you will need to undo the battery case, there is a small pin at the bottom.
So what you need to do now is press the button on the neoFlo, while doing that, close the battery case at the same time. The unit should activate.
After a moment you should se CL appear on the screen.
When you see CL on the screen, release the button, then press the button again on the neoFlo until you see the following appear on the screen.
When you see this symbol go solid, release the button. The neoFlo is now reset. It will need to be paired back to whatever it was connected to previously, the neoHub Gen 3 and RF Switch V2