You have to insert it in both ears deep and hold there for a minute or two until you hear a beep or vibration (varies according to models ) and i repeat do not and i mean DO NOT try to move your head (or any other parts) until the process is complete .
I work in a manufacturing environment and put in ear plugs every day. Generally this is a two handed procedure, where you pull your ear back to get a good angle to correctly insert the plug, but after doing it multiple times a day, ever day, for years, you get pretty good at double fisting your own ear canals.
Every once in a while, you hit the angle and risk resetting yourself to factory settings.
The real risk is losing the fucking thing up there, and it really feels like you might for a second.