I would not recommend that configuration as the throughput of the 202 is only about 30 Mbit/s; quite low by modern standards.
However if you want to do it, here is how:
1. Connect the LAN port of the OBi202 to a LAN port (not WAN) of your router.
2. Do not connect anything to the WAN port of your router.
3. Disable the DHCP server of your router.
4. If setting any of your other equipment to have a static IP address:
4.1 The IP address should be in the 192.168.10 subnet
4.2 The subnet mask should be 255.255.255.0
4.3 The gateway should be 192.168.10.1
4.4 The DNS server(s) should be 192.168.10.1 and/or whatever other remote servers you want (eg Google's 8.8.8.8, OpenDNS 208.67.222.222 etc)
4.5 Check and if necessary amend the range of IP addresses in the 202's DHCP server's pool.
5. If you need to access the router's configuration pages (eg its Wi-Fi settings) change its IP address to be in the 192.168.10 subnet.
6. The 202's configuration server is at 192.168.10.1.