Follow the below instructions for create your Sendgrid API Keys
Login to Sendgrid at https://app.sendgrid.com with your credentials.
Expand Settings on the menu on the left and click on API Keys. You would see the list of API Keys already created for this account.
Create a new API Key and name it as Daton or by any other name which identifies the purpose of this API Key.
Select Restricted Access for this API Key and further select Read Access for each individual API. Please note that Daton would require only read access to extract the data from Sendgrid.
Copy the API Key and save it someplace safe as it will not be displayed again. You are required to provide this API key while integrating Sendgrid on Daton.