First, head over to: https://app.datatrics.com/integrations/sendgrid/ and click on "install"
After clicking install, you will see the following screen:
You can create an API key and token the following way, first log into your SendGrid account.
From the left side menu, click on Settings, then on API Keys.
Click the Create API Key button on the top-right of the page to create a new API key. A new screen will appear.
Inside the API Key Name field, enter a name for your API key.
You can then enter the correct list ID.
After these fields have been entered, the integration has been completed.