You may want to add your own JavaScript code to your Clickthroo landing pages - to do so is very straightforward.

When in the Clickthroo Editor you will see a tab called 'JS'. Click this.

In the pop-up window select the Script you would like to edit from the left-hand side. Now all you have to do is select the section of the code where the JavaScript should appear and paste the JavaScript code into the box.