The Things Outdoor Gateway - IP address setup

I’ve been following the setup guide for TTOG (https://www.thethingsnetwork.org/docs/gateways/thethingsoutdoor/). Under the following step:

“Enter the IP Address assigned by the Gateway into the web browser to acquire access to the ODU GUI interface. The IP address is likely 192.168.2.13 . The configuration page should look like this:”

But when I look up 192.168.2.13 on a web browser I just get “This site can’t be reached”.How do I find out the IP address for my gateway?