Simple to do, hard to locate the information on how to.
Hopefully you’ll find this a lot easier..

Navigate to :

Configuration, HTTP Service, Virtual Servers, server

Scroll to bottom of page :
Add Property

Name :
redirect_1

Value :
from=/{name of webapp to redirect} url={URL to redirect traffic to}

(dont include the ‘{‘ ‘}’ brackets)

It should look something like this :
from=/mywebapp url=http://www.google.co.uk

Click ‘Save’ button.

Done!