To get your browser to use WebMask, you'll need to tell it to use your own machine as a proxy. The reason you need to do this is explained here.
Explicit instructions are given for the following browsers:
If you're using a different browser, the exact steps taken will differ, but the overall process will be similar. General details are given here.
If in the above step you found that WebMask already used a proxy, then you will have written down the host and the port for that proxy. You need to follow these instructions to tell WebMask about them.