I had a employer insurance as well as Medicare coverage during the same time, how do I file? it only allows me to choose 1 or the other not both

You do not need to enter the details of your employer insurance or your Medicare.  All you need to do is to answer Yes to the 1st question, that you had health insurance for those months (or all year).  The 2nd question asks if you were covered by Obamacare, a Marketplace plan, or a plan that sends a 1095-A.  You should answer No to this question. 

The only forms that get entered into the Health Insurance section are 1095-As.  Neither Medicare nor your employer reports coverage on a 1095-A, so you only indicate that you were covered for those months that you had the coverage.  You may have received a 1095-B or 1095-C for the type of coverage you had.  These forms are kept with your tax records but they are not entered into TurboTax.  For non-Obamacare plans (like you had), you simply tell TurboTax that you were covered.