In order for Google AdWords' conversion tracking to work, the tracking script must be placed on the final page of your funnel. This is usually your thank-you page and by default in Unbounce, it will be your form confirmation dialog.
To configure AdWords conversion tracking to work with the form confirmation dialog:
Access your Google AdWords account and click Tools and Analysis > Conversions
Create a New Conversion or choose an existing conversion and follow the steps to create your tracking code then Copy it (see Google AdWords' Set Up Instructions for more information).
Load your page in the Unbounce editor and click the Form Confirmation Dialog tab in the upper left of the editor to edit the form confirmation dialog page.
Click the Scripts button in the editor toolbar to open the scripts dialog.
Name your script, for placement choose Before Body End Tag, and paste in your AdWords conversion tracking code
Save and republish your page.
AdWords will then track conversions on your Unbounce landing page.
Note: AdWords will often take up to 24h to reflect a conversion. If you test your page, you may have to wait up to 24h to confirm that the script is working correctly.