Is the HSA in your wife's name? If the HSA is in your name and you are on Medicare, you (nor your company) are no longer eligible to contribute to your HSA.
Assuming that your HSA is properly set up, you can indicate the employer contribution here:
To enter pre-tax contributions that were not reported with code "W" in box 12 on your W-2, go to Federal Taxes->Deductions & Credits->Medical->HSA, MSA Contributions. Start the HSA interview.
Go to the screen entitled “Did your employer tell you about any other contributions?”. Even though the line underneath the heading makes a comment about contributions made to a previous year, answer “yes”.
This will show three more questions at the bottom. The last question is “Employer and payroll contributions not reported in Box 12 of your W-2”.
Enter your pre-tax employer contributions that were not entered with code “W” in box 12 on the W-2 here in the space to the right.
NOTE: you haven't mentioned if these employer contributions were pre-tax or after-tax. Are you getting a 1099-R or a 1099-MISC for these contributions? If so, you would enter this amount on the screen entitled "Let's enter [name]'s HSA contributions" on the line that reads "Any contributions you personally made (not through your employer)".
