I have a mutual fund 1099 DIV, it only has a value box 1a.

This would be entered as income for Form 1099-DIV. You would enter the amount in Box 1a, Total ordinary dividends.

The easiest way to enter Form 1099-DIV is to open your return, search for 1099-DIV, and select the Jump-to link at the top of your search results. That'll take you to the screen where you can enter your dividend income. Or you can follow the instructions in this TurboTax Help article for another way to enter Form 1099-DIV.

Under Wages and Income, Investments and Savings - click Start.