In Marketing Cloud, navigate to setup
Under Platform Tools, expand Apps and click Installed Packages.
Click New. Give the package a name and description so that you can easily identify it as your first test package.
Save the package. After the package is saved, you can view the package details. Under Components, click Add Component. In our case, we will select API Integration.
Now we need to choose the Integration Type: Web App, Public App, or Server-to-Server. These types of integrations use the OAuth 2.0 protocol to obtain an access token. A little info about each type:
|OAuth Grant Type
|Web Apps make API requests in the context of an end user. These integrations are issued a client ID and client secret because they can maintain the confidentiality of a client secret.
|Public Apps, such as single-page or mobile applications, make API requests in the context of an end user. These integrations are issued only a client ID because they cannot maintain the confidentiality of a client secret.
|A server-to-server integration performs tasks on behalf of the integration, without an end-user context, user interaction, or user interface.They make API requests in the context of a service account instead of a user account. These integrations are issued a client ID and client secret to use with the Client Credentials grant type.
In our case, we will select Server-Server and click Next
Now we are at the final step of adding a component, where we are required to set the properties. Enable the scope for the platform functions we are including within the integration. What is the scope of this API integration – Update contacts? This scope represents a group of permissions which ensure the API request can access the appropriate functions. The properties can also include redirect URIs for web and public apps.
For our example, we will select Write access for both Audiences and List and Subscribers under Contacts. After setting properties click Save
Here is a very good video tutorial on Setting up Installed package for Marketing Cloud API’s: https://www.youtube.com/watch?v=BynX5IRomRg