To duplicate an existing web form, go to Automation > Web Forms

Find the Web Form you want to duplicate (clone) in the list and click the grey 'Duplicate' button. A dialog box will appear asking you to confirm that you wish to duplicate - click OK.

Your Web Form is now duplicated (cloned) as 'Copy of x', x being the name of the form. You can edit the name and options for this form by clicking the grey 'Edit Form' button.