The Spyglass is primarily Gesture and Contact based. It is not Desktop compatible for this reason
Make sure that the ‘Visible’ toggle in the Spyglass Menu of your Radial Expressions Menu is enabled and that the spyglass is visible on your avatar in it’s storage location, this is normally on the Upper Right Leg but may be different on modified versions.
To grab the Spyglass make a Fist Gesture with your right hand while holding it near the storage location of the spyglass. You can put the spyglass back by putting the hand holding the spyglass in the Storage location and making any gesture other than the Fist Gesture.
If for some reason you cannot access the storage location or just want to toggle the Spyglass to be in your hand without grabbing it you can also use the ‘In Hand’ Toggle in the Spyglass Menu.
With the spyglass in your hand bringing the eyepiece of the spyglass up to either of your eyes will override that eye with a view of what the spyglass is seeing. Note: this is Local Only so only you can see through the spyglass. To adjust the zoom you can grab the eyepiece of the spyglass and pull to extend the spyglass. The more extended it gets, the higher the zoom.
If you can’t grab the physbone for extending the spyglass you may be grabbing it with the hand that is holding the spyglass if you’re still making a fist with that hand. You’ll need to let go with that hand in order to grab it with the other.