I am filling in the HSA information and its asking for personal contributions from box 12. But there is 12a, 12b, 12c, 12d. Which amount should I use?

You HSA contributions are usually reported on your Form W-2 in Box 12 with a Code W. Do you have an item in Box 12 of your Form W-2 with a Code W?

if your HSA contributions are listed on your W-2 (box 12 - code W), DO NOT list it again!! it is a common error. 

personal contributions are NOT the ones listed on your W-2.  they are additional contributions that you may have made directly to the Administrator.