So look up the IP address of the computer that you are mining from (use https://www.whatismyip.com/ or ipconfig in the windows command line prompt), enter the IP and change to whatever value you want.
If you are using a VPN or something else that changes your IP address, you need to enter the original IP address when the miner started mining. In this circumstance, as you probably don't know it, stop your miner, wait a period of time until the miner is no longer showing up on the mining pool, and restart the miner, and it will ask for the IP address you have right now.