Employer contributions to your Health Savings Account are reported on Form W-2, Box 12 with a Code W. An amount entered here will flow to Line 7, Column C of California Schedule CA. The amount is then added to the income total on Line 16 of California Form 540.
Continue to the Wages - W-2 - Information screen for Boxes 12-13 and select W - Employer contributions to your Health Savings Account from the drop-down menu for Box 12. If you select Quick Entry, scroll down and enter W for the Box 12 code.
Per the California Instructions for Schedule CA (540):
Employer health savings account (HSA) contribution. Enter the amount of any employer HSA contribution from federal Form W-2, box 12, code W on line 7, column C.