If you already played around with the Sitecore OrderCloud portal (https://portal.ordercloud.io/), you should see the Me and my stuff section there.
Sitecore OrderCloud documentation says:
With an understanding of the robust visibility options involving roles, group-level assignments, Buyer-specific pricing, "Active" bits, and the like, you might be wondering, where are all these rules actually enforced? This is the job of the resources that begin with "me". Whether authenticated as yourself or impersonating as someone else, you see only what that user is allowed to see. A good rule of thumb is that, other than authentication, you should be able to build an entire Buyer experience using only endpoints that start with "orders" or "me".
It’s a sort of powerful feature available in Sitecore OrderCloud, which provides a possibility to switch between the different contexts of users to quickly get information about the currently authenticated user, the Me resource provides a set of admin endpoints for personal resources (Credit Cards and Addresses) that only that user can see. It also provides ways for a user to update or change their information.
The first time when I tried to work with Me resources, I was confused a bit, because it was not clear, how to switch between different contexts. I would like to share how to switch the context.
You have to navigate to Dashboard and select the Marketplace:
Once the marketplace will be selected, you will be redirected to the Console page. On this page on the left side in the top, you should click on the selected Marketplace and a popup will be appearing:
Since the Marketplace is selected, you can select the API client which you need and in the third column, you can select the User Context. For example:
Once the User Context is selected, you can start to use Me resources in the context of the selected user. In my case, I just selected the Marketplace and didn’t know that there is a popup where you can select the user context.