The AEM integrating with DTM requires the use of a DTM account API-token. The API key is only visible to users that have authenticated via the marketing Cloud and Adobe employees.
To retrieve you API token, follow the procedure below:
If you are unable to retrieve you own API token, you can contact Adobe Client Care or you can reach out to Adobe DTM Community Team (Jantzen Belliston). In order to retrieve your token, you'll need to provide your DTM company name and the email address associated with your DTM user.
Client Care can be reached by having a supported user email firstname.lastname@example.org
Since the API token is essentially a password, Community team will be unable to send API token via email.