1. Firstly, go to the Dock or the Utilities Folder and click on the AirPort Utility.
2. Then you should click on AirPort Express > Edit.
3. Now choose the Internet tab via the upper bar of the new window.
4. In the DNS Servers fields, you should enter the AirPort Express primary and secondary DNS servers.
22.214.171.124 - EU DNS
126.96.36.199 - US DNS
Note: You should use the closest server to your real location as the primary DNS server and the second closest server as the secondary ones for AirPort Express.
5. Then you should click Update and wait till AirPort Express router will restart.
6. Last but certainly not least, restart all the devices that are connected to the AirPort Express and that you’d like to use with KeepSolid SmartDNS.