When you get your throw lever it will have a cap on it. 

1. Remove the cap

2. Slide throw lever one the end of the scope. If it won't fit over the lens cap or objective lens, you can slide it over the focus knob. They do open quite a bit before they will break. 

3. Align it to the groove(s) in the focus knob. Squeeze tight and reinstall cap. Some caps might be a little tight, this is normal. Hearing sounds is also normal on tight caps. 

NOTE: If your cap doesn't fit properly, contact us for help. It is possible you ordered the wrong cap or that there is another issues and we will get it corrected for you.