If you enter an IP address in IP Restrict for a user, the selected User will required to login to the software from that specific computer or IP address.  

To find the IP address for a specific computer, cut-and-paste the URL below into a Web browser:  

https://support.microsoft.com/en-us/windows/find-your-ip-address-in-windows-f21a9bbc-c582-55cd-35e0-73431160a1b9

Upon launching the software, left-click on Manage;

observe the next screen, defaulted to the first User;

select the desired user (in this example, the second one); &

to complete the process...enter the IP address, re-enter the Password in both fields, and left-click Save: