How to set default user at login screen? When I turn Mac on, it goes to another user with space for their password. I must wait until an arrow appears to login to my user account. How do I change the default to my user account? HELP! Thank you!!

Hello!

How do I set default user at login screen?

When I turn Mac on, it goes to another user with space for their password. I cannot delete this user (IT department where I work) because it must remain as a requirement and they still need access to my computer as an administrator. This is an example of what the screen appears like but this is from Google Images (not my computer or image):

I have to wait patiently for an arrow to appear. See arrow that points to the left in the image below (Again, not my image but from Google Images):

When the arrow finally appears, I am able to click the arrow where I am taken to a screen where I am FINALLY able to type in my own username. See image below (from Google Images):

I would like to either set my own user name as the default username when I go to login (so that I merely have to type in my password), or add myself as a second user to appear at the login screen. See example of second idea below (from Google Images):

Thank you! I have tried so many different settings on the Users & Groups... I have exhausted all of the usual ways that I utilize for a Mac question as I am an avid apple user.

Thanks again!

iMac

OS X Version 10.8.3