I am looking for Box 12 on my W-2. There is a Box 12a, 12b, 12c, 12d. I'm trying to enter my HSA contributions but the instructions attached don't show any HSA info.

Box 12 is divided into 4 boxes - a, b, c and d - in order to give employers plenty of room to enter the information that they need.  Your HSA info should appear in one of those.  If it does not then you need to contact your employer.

@denisemarie-b 

You do not enter your HSA contributions on your W-2

To enter your medical expenses -

Click on Federal Taxes (Personal using Home and Business)
Click on Deductions and Credits
Click on I'll choose what I work on (if shown)
Scroll down to Medical
On 1099-SA, HSA, MSA, click the start button