The easiest recommendation on how to reset your wireless router or your modem is to unplug the power supply from the back of the device for 10 seconds. After 10 seconds plug your device back in. Plug your modem in first and wait for that to boot and then plug in your wireless router.
CAUTION: BE SURE THAT DISRUPTING YOUR INTERNET SIGNAL WILL NOT INTERFERE WITH ANY OTHER EQUIPMENT OR DEVICES IN YOUR LOCATION BEFORE DOING THIS.
Otherwise you will want to contact the support center of the brand of your device for specific information about your device and how to reset / reboot the device.