You can use multiple ways.
Example 1:
Text file
if ($read(textfile.txt,nw,$nick)) { }
Example 2:
Dynamic list
var %list Name1 Name2 Name3
if ($istok(%list,$nick,32)) { }
Example 3:
Static list
if (($nick == name1) || ($nick == name2)) { }
You can also combine this with your isop statement.
Example 4:
Combined
if (($nick isop #) || ($read(textfile.txt,nw,$nick))) { }