If you are only on Part A, you will need to add Part B. There are 2 forms that need to be submitted to Social Security (the administrative arm of Medicare) to activate your Part B to provide you with a special election period onto Medicare health and drug insurances due to the loss of your current employer insurance coverage.
Once your Part B enrollment is approved, you can choose to enroll onto a Medicare Supplement/Medigap policy and stand-alone drug plan /or/ a Medicare Advantage/HMO plan.
Please check with your wife’s employer to confirm that the drug benefit under the retiree plan is creditable drug coverage under Medicare. Once you enroll onto a Medicare stand-alone drug plan or Medicare Advantage/HMO plan, should Medicare question whether the drug coverage you’ve been on was creditable drug coverage, your new prescription drug plan carrier will ask you to provide them with verification that the employer’s drug coverage was creditable under Medicare. Individuals who have not had creditable drug coverage since turning age 65 are eligible for a monthly penalty (1% per month based on the national average) which they will carry in perpetuity.