Here's how to install a NATO strap.
Step 1: With the watch face facing towards you, feed the end of the NATO strap downwards through the gap between the spring bars and the watch face.
Step 2: Next feed the strap end upwards through the opposite side, pulling it through until the strap is pulled tightly against the underside of the watch face.
Step 3: Feed the same end of the strap as you've pulled through, into the fixing that's half way along the other side of the strap.
Step 4: You can now use your Nato strap!
If you have a very thick strap, you may need to place the strap in place with the spring bars off initially.
If you need a new Nato strap, consider choosing from the unique range at Nato Strap Store here.