Go to your Optingun dashboard, and click on Drip icon, this will reveal "API Connect" button, clicking this button will redirect you to Drip for authentication, now login to your Drip account and authorize Optingun to connect your Account via API

Go to your forms or create new form, and navigate to "Integrations" tab in the left menu, and from email software selector, select Drip, this will connect to Drip in real-time and list you all the campaigns available in Drip and also gives you a field to enter tags to attact to contacts, after selecting campaign and entering tags(if wanted) click on "Add Integration" button to add, now you should see the rule description on right side tab, now update your form by clicking the green "Save/Update" button on left side menu as shown in the picture below with numbering.

This is all you need to do to connect your forms with Drip, enjoy using it.