You need the API key to integrate Clearbit with Vtiger CRM. You can copy the API Key from your Clearbit account while you are setting up the Clearbit in the CRM.

Follow these steps to integrate Clearbit with Vtiger CRM:

1. Login to your CRM account.
2. Click the Menu icon on the top left corner of the screen.
3. Go to Essentials.
4. Click Contacts to go to the Contacts module.
5. Click the Settings icon on the top right corner of the screen.
6. Click Clearbit Settings.
7. The Setup window is displayed where the Clearbit API Key has to be entered.
   1. If you do not have the Clearbit API Key, click the here link.
   2. Log in to your Clearbit account. 
   3. Copy the Clearbit API Key from the Your API key window.
   4. Paste/enter the Clearbit API Key in the Vtiger CRM Setup window.
   5. Once the Key is saved, you receive the success message as displayed below. And you will be redirected to the Contacts page.

8. Select the contact whom you want to know more about and who has an email address.

9. Vtiger CRM provides the Clearbit button on the top right corner of the screen. Click the Clearbit button for Integration.

10. The Clearbit Integration looks like the below image with all the available customer data.