Your clients received a 1099-DIV from their brokerage account, and there are capital gains distributions listed in line 2a. Does that mean that they should be entered as dividend income? That may seem to be the right answer, but not so fast my friends!
It may sound strange, but the IRS considers capital gain distributions as long-term capital gains no matter how long you've owned shares in the mutual fund.
Capital gains distributions from mutual funds are reported on line 13 of Schedule D, and are lumped into net long-term capital gains/losses on line 15, despite how long you may have held that mutual fund. 
You would enter any capital gains distributions in the "Long-Term Capital Gains and Losses" Worksheet. You can access that worksheet by clicking on the pencil icon circled below for "Long-Term Capital Gains" in the "Schedule D Income" section of Scenario Analysis.
From there, you would enter those capital gains distributions in the "Capital Gain Fund Distributions" line highlighted below. In this example, $10,000 of capital gains distributions were included in the total long-term capital gains in this scenario.
If you have any other questions about enter capital gains, check out our Modeling Capital Gains article or Contact a member of our Support Team!