MI does not tax Social Security. You are supposed to enter your SSA1099 on your federal return. Information flows from the federal return to your state return. TurboTax uses the tax laws of your state and puts the necessary information on the MI from your federal return. SS will not be put on the MI return, since your state does not tax that.
Go to Federal> Wages & Income>>Retirement Plans and Social Security (SSA1099 and 1099RRB) to enter your SSA1099.