Connecting your Sendlane account with Optingun forms is very easy.
Go to Sendlane dashboard and click on Account on left menu, and select Developer page, there you will have your API credentials, copy the two keys and subdomain from this page.
Go to create or edit your forms and navigate to settings page, you will see a tab for integrations.
Click on Sendlane icon from the App list there. If you have not connected your Sendlane account yet then this will ask you for your Sendlane API details, if API details area already saved then it will go to next step directly to list you contact lists.
Paste your API Keys and account subdomain in Optingun Sendlane Integrations settings page, and click "Save and Connect Sendlane", this will validate your API details and if they are correct it will connect to your account and load your contact lists.
Select a contact List from the select box and click "Add Integration", your new Integration will be listed below that settings box.
If you want to add leads from this Optingun form to a new contact list, go to Sendlane dashboard and Create a new List. After creating new list in Sendlane, comeback to Optingun dashboard form builder, and click "Refresh Lists" link, this will pull the new list that you have just created, select the list you want and click "Add Integration"
Do not forget to save your form after all these changes. Once this form is saved, your leads from this form will go the Sendlane Contact List you selected. And thats all it is to connect Optingun forms with Sendlane.
You can also watch this video tutorial about the same process.