If you haven't already, you'll need to sign up for an Omnisend account.
Setting up your Omnisend API key
Navigate to the API Keys screen, by clicking the your name in the top right corner and selecting "Store settings" in the dropdown. Next, click 'API Keys' in the menu on the left.
Create a new API key and be sure to select the option to only give permissions to add new subscribers.
Paste in the API Key and URL on your settings page under "Integrations"
You're all set!
💡 Tip: You can now head to the opt-in form support article to add/complete your opt-in form.
Adding a Tag
When adding a new contact to your audience, you can specify any tags you would like to be applied. This is useful for organizing your contacts internally. Check out Omnisend's Working with Contact Tags for more info on tags.