Windows: 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.
Mac: Open your return and select the Search icon. Search for 1099-DIV, select the form, then OK. That'll take you to the screen where you can enter your dividend income.
Another way to get there is to select the Federal Taxes tab (or Personal if you're using Home & Business) and then select Wages & Income. If you see the How do you want to enter your income? screen, select I'll choose what I work on. On the Your 2020 Income Summary screen, select Start or Update next to Dividends on 1099-DIV.