How to split lan into two networks

i have a "lan" interface and firewall. This lan has wireless connection plus a server on physical lan port 1. The network is in ip range of let's say
I would like to isolate the two into two different networks (say, wireless on ip/network and the server on ip/network split the into two ip ranges), but can' t seem to grasp on how to do this. Any suggestions?

Check out how to configure guest WiFi, this is more or less your solution:


but instead of connecting it to the wireless, where do i connect new network to? br-lan?

If you want to split your networks, you will connect one network (i.e. the guest network, broadly speaking) to wifi and leave the other connected to ethernet. Or vice versa -- move the ethernet port(s) from br-lan to your new network (possibly via another bridge).