Log into your account, click on the blue "Reroute" link at the top of the page. Inside this page you will find the diary icon and a link to setup Diary Rerouting for your Flextel numbers. Once you have clicked this link, simply fill in the form provided with your desired settings and press submit. The entry you create will then be shown in a table below the form.
Click here for a more information, including details of each entry field in the form.