Before you start your install, its a good idea to head over til your pipedrive account and retrieve your API token.

Go to https://{yourdomain}.pipedrive.com/settings#api (replace {yourdomain} with your own Pipedrive domain). Copy the token in the highlighted box:

Once you have installed the Pipedrive App from Zendesk Marketplace paste the API token from Pipedrive in the box called API token in the App Configuration:

Proceed to How to add pipedrive customfields to add any custom fields you might have created in Pipedrive. If you don't have any custom fields in Pipedrive just click Save Settings.