-open WinBox and go to IP/DHCP Server/Leases
-right click client that will be authorized to connect and choose Make Static
-Click DHCP tab and click 2x default
Change Address Pool to static-only
Let say, you want to add new client, please change Address Pool to dhcp first, then repeat the same process above.
Client that is not authorized, won’t be allowed to connect to your wireless
Add the client MAC address manually in IP/DHCP Server/Leases