Here's a guest blog post by Matthew Burkett on configuring the Merlin router firmware for OpenVPN.
So starting from the point of opening the box or using the reset button, when you first power on the device you will need to enter the basic information. Secure username and password for the router login, wireless SSID (Name) and password for both 2.4 and 5 Ghz channels, and your internet connection info if it was not automatically detected by the router. At this point you should have a fast useable router with great wireless coverage, if you are a standard user congratulations your done. Get on face book and tell your friends, if you are like me however you have only just started.
Merlin firmware installation