How to set up a dd-wrt router so that it takes the Internet from another router and distributes it on a different subnet?

Question

Network administration

Hello everyone, I can not solve this problem.
There is a modem / router (192.168.1.1) with Wi-Fi that distributes the Internet. There is a router with Wi-Fi and dd-wrt which should also distribute the Internet, but on the 192.168.2.1 subnet.
How to configure a router with dd-wrt so that you can connect it with a cable to the lan port of the first router (192.168.1.1) and when connected to a router that has dd-wrt via lan or wifi, the devices receive ip from the 192.168.2.X network and have internet access?