Can't log in vSphere Client

Hello Community,

I'm a newbie at getting to know vCenter. After installing vCenter I can log into the Appliance Management but can't for the vSphere client. I'm am confused to what the login name is that I know I created. I'm really having a dumb moment here and I apologized in advance!

I used both marked in yellow in the (attachment) but none work that I created. I know this should be easy but it's not for me.

Any help would be much appreciated.

Thanks in advance everyone