How to limit WP admin access to single IP in CP/OLS

Can anyone tell me the best approach to limit access to file ‘my.domain/wp-admin.php’ and or folder ‘my.domain/wp-admin,’ to an IP or multiple IP’s?

Pretty sure it is done via the vHOST file in CP but I can’t find the syntax to use. Or is it only done via the OLS web ui?