To setup an API Key for your ExpenseIn API integration, you'll need to have first determined which permission(s) the API will need when accessing ExpenseIn.
You'll be able to cross-reference the information the API requires access to with the required permissions on the Developer Centre. For example, in order for the API to retrieve invoices using an invoice ID, the API key will need the Finance user permission.
Once you're aware of the permissions needed, head to the Admin area of your account and select the Integration heading.
Then navigate to the ExpenseIn API tab and select New API Key.
Select the required permissions for the API Key and click Add.
You'll now have an API key setup ready to be used. You'll also be able to configure and regenerate the key at any time from the Admin area.