I have a website that's built and a dd-wrt router. I need someone to help me configure the router

i have a website built in react. Which has 3 pages one to accept terms and conditions ,one to collect username and email the other to show ads i need the user to be redirected to my page when he tries to login into the Wi-Fi using a captive portal then redirected to my page after watching the ads. the user can use the Wi-Fi