In the K-1 entry section, there is a screen "Describe the Partnership".  On that screen is a line you need to check for "Disposed of a portion of my partnership interest in 2019".  When you check that box, TurboTax will present you with the questions to report the disposition and correctly report the gain on your tax return.

Click the "magnifying glass Search" icon on the top row, enter "k-1" in the search window and press return or enter, and then click on the "Jump to k-1" link to begin edit the entry for your Schedule K-1.

Here is a screenshot of the TurboTax screen you are looking for:

One of the more important pieces of information that will be needed is your basis in your partnership interest.  Hopefully you have maintained this information.  Unless you have this, you will not be able to determine your overall gain or loss on this investment.