You will enter military retirement pay in the "Income & Expenses" tab.
Scroll down to "Retirement Plans and Social Security"
"Show More"
"Start/revisit" the "IRA, 401K, Pension withdrawals (1099R)"
"Add a 1099R"
Select the "Financial Institution or other Provider" option
Military Retirement pay is a non-qualified plan and falls under that catch-all category.