In VS2015 how & where do I configure the account that accesses the SharePoint Site/agile team functions?

Question

Locally installed TFS2013, VS2015 and VS2013 using SharePoint services.

So far the development system is kind of OK, meaning I can create a collection, create a team project within a collection, add a new solution to that, run it, do a Check In and the SharePoint site shows the project code, etc. I can also create work items at the SharePoint site and from within Visual Studio.

But I'm having difficulty understanding how the user accounts are interacting. On my development workstation I logged in with a normal domain account. But I do not see work items assigned to that user name. I only see work items if they are assigned to the system Admin account.

I would have expected VS would be operating under the user account that I logged into Win10 with, but it seems to be operating as though VS is logged in as the system Admin.

Why is that? Is there a place where VS sets data that tells TFS what user name it is operating under? And, of course, I may be asking the wrong question because I don't understand the problem, but this is how it appears.

Added after initial post for clarity

This panel shot shows where the Work Items were not showing up for the user under Available Work Items. Because of the issue identified in the answer below, only work items assigned to Admin were present. But after clearing the cached credentials the work items displayed correctly according to the proper account, no longer acting as Admin.

Answer 1

This may due to the VS had cached your system Admin account.

The simplest way is to delete the related credentials which stored in control panel > Credential Manager> Windows Credentials

Then reopen the VS and try to connect to TFS server. It will pops up a credential window, just type your login domain account.