You can find this feature in the "Access Control" tab of a site's configuration.
Within the same rule, you can write one or more URL regular expressions (refer to the tooltip for the syntax):
On which you can authorize one or more IPs (or subnets):
Finally, you can choose to analyze or not ("Analyzed" or "Passthrough" mode) the requests that will match this access control rule, as well as to add a comment.
Don't forget to activate the rule with the toggle button!