We have two kinds of Infusionsoft integration:
1.) Email autoresponder integration, for capturing leads and creating followup sequences for your optins (the settings for this can found under My Account > Settings > Email Integrations).
2.) Payment processing integration, right on your ClickFunnels order pages, using Infusionsoft (the settings for this can found under My Account > Settings > Payment Integrations).
This article below will cover the first kind.
Access Your Infusionsoft API Key
In order to integrate Infusionsoft into your ClickFunnels pages you will need your API Key. To access this, log into your Infusionsoft account and go to Admin > Settings > Application. Then scroll down to the API section. Enter an API Passphrase that will be used to generate your API key if you haven't already. Click Save and your API Key will be generated. Copy the API Key to a safe area as you will need it in a future step.
Create New E-mail Integration
Inside of ClickFunnels, got to My Account > E-mail Integrations and click New Integration.
Enter Your Settings
Name the integration and select Infusionsoft API from the drop-down. Then enter your Infusionsoft subdomain. Make sure it is just the subdomain and not the whole thing. For example, if your Infusionsoft app is at "example.infusionsoft.com", then you would just enter "example". After that, paste your API key from the first step.