tl;dw? Hold the reset button down for 10 seconds. Let go, power light will go off for a bit.
How to factory reset a D-Link DWR-953 4G modem. Shows you where the reset hole is and how long to press it for, also shows what the lights do and how long it takes for the router to start responding on the network again.
This procedure will be helpful if you have forgotten your login details for the router.