Hi @official_99, at the moment, are you looking for a link between your Developer Account and how this works within your live Business (Production) Account? If so, the way developer accounts work is that you create an app that does something. This app can then be installed by any number of live production accounts via OAuth (not api key). This is where the "connection" happens. Once this app is installed, whatever the app does will be able to perform those actions on each individual production account that is installed in. Sometimes people create apps as a one off solution, or for mass consumption like Salesforce or SurveyMonkey.
In your case, it just seems like you'd like a contact to be created after they do an action. With this, since the contact's api does not support front-end (AJAX) requests, you'd need a request to be sent to your servers where your servers could then submit a request to the create a contact endpoint. If you're an enterprise customer, you might also want to try using Events