You give permission to the command by using `ulx groupallow group_to_allow "ulx adduser"` in console. If you want to restrict the groups they can add users to, it'd be `ulx groupallow operator "ulx adduser" "* group1,group2,group3"`, where operator is the group you're giving permission to use ulx adduser to, and group1, group2, group3 are the groups operators can add other users to. If you want to prevent them from changing groups of already-added admins, you'd use `ulx groupallow operator "ulx adduser" "!%admin group1,group2,group3"`.