Amazon developer ID

Question

I would like to start developing amazon integration for my website I would like to integrate products, orders etc and I understand I have to use Amazon MWS for API.

To start using MWS I created a developer account Now the amazon seller has to authorize me by inserting my developer ID.

I can't find IT.

I contact amazon support and they told me to go

Settings -> User Permissions -> Click on visit developer credentials.

But if I go to User Permissions I only see the users list with the possibility to add or edit a user.

In this image info@e-miko is the owner of the seller account (and I'm logged in as him) while Martina is me, the developer. As you see no Developer id is visible.

Any idea?