Installation is fairly well explained in the manual and relatively simple.
Simply hook the counter at the post (there are very resistant elastic supplied with)
Must then hook the wheel sensor on the fork and the magnet on a beam
Be careful, remember to respect 70cm max distance between the meter installed on the stem and added sensor on the fork.
Then 5mm between the magnet on the spoke and the sensor on the fork and you're set!
Also consider changing the counter parameters in the circumference of the wheel (if your performance will be biased). The easiest way is to do make a full turn the wheel to the ground and measure the distance between the two points. Take the valve as a benchmark, it is very convenient.
Good trip :)