Test it first before installing to make sure it works and figure out which direction and orientation the disc has to go.
Turn the bike upside down, plug in the connector and switch on the bike. Rest the sensor on the edge of something, like a table, stool, book or anything like that. Stick a small screwdriver handle or anything the correct size into the disc, then twizzle it round over the sensor. If you're lucky, it will work in one direction one way up and the other direction the other way up. If you're unlucky, only one of those will work, and you hope it's the right way for the side you want to install it.