The easiest way to fit the earphones is to first remove the cable so you are just holding the driver in one hand and the Snug in the other.
Do make sure you are trying to insert the Right earphone driver into the right Snug ! and vice versa with the left. Obvious but a common first mistake !
Have a look inside the Snug and you will see a small hole where the Sound Outlet Bore hole is at the end of the driver encasement fold.
This is where the drivers sound outlet bore must be positioned and then pushed down the sound bore into the Snug.
Position the Drivers sound outlet next to the entrance of the bore hold in the Snug body.
Push the Drivers sound outlet tube into the Snug bore hole. As you do this the driver will nestle inside the encasement area of the Snug.
As you push a little further, the sound outlet tube will go as far as it can and the driver body will be sitting securely within the Snug.
Beware that you do not split the Snug body. If it is all tight then use a little of the supplied Dreve Crème on the driver body to make it slide into the Snug.
Watch out if you have sharp nails as they can slice the silicone. Only remove the Snug very occasionally to clean.