Select Preferences from the Edit menu.
In the tree on the left, under Advanced select the Proxies item.
If the HTTP proxy is already specified, and the Manual Proxy Configuration box was checked to start with, then you need to write down the host and the port that it is set to use. Later you will use these to tell WebMask about this existing proxy.
Set the HTTP proxy to use address 127.0.0.1 and port 8080.
Setting up your browser to use WebMask