If you're referring to the Cox App, use the following steps:
After signing in to the Cox App, the main screen is displayed. Click the right-pointing arrow in the shaded section labeled "My Internet/Cox High Speed Internet". Scroll down to the modem section. Underneath the make, model, and MAC address of your modem is a "Reset Modem" option. Clicking on this option should open a browser window and take you to www.cox.com/.../refresh-modem.cox. Click on the blue "Reset Modem" button. You should receive a green checkmark and a confirmation message once your modem has begun the reset process.
-Becky, Cox Support Forums Moderator