First run

If this is your first run of the WebUI then you've been redirected here because you haven't specified any Dispatchers for the WebUI to use.

Dispatchers

You can start a Dispatcher by running:

arachni_rpcd

in a terminal.

This command will fire-up a Dispatcher which will, by default, bind to:

localhost:7331

Input this URL in the 'URL' field and press "Add".
After that you should be able to use the WebUI to perform scans.

You can find more information about setting up Dispatchers here.

Edit Dispatchers

This screen allows you to add and remove Dispatchers.