API key to integrate a field with Mailchimp

I want to integrate the "job booked" field in ServiceM8 into Mailchimp so that when we enter the date the job is booked for, it triggers an email going out from Mailchimp to confirm the booking. I have researched it and I can use Make.com to integrate the 2 systems but I need the ServiceM8 API Key. It looks like I need to set up a developer account first. If I do, does this impact the main account in any way or is this a separate account? Where and how do I create the API key? Thanks