Do I need to include my K-1 (form 1065) on my tax return when there was a loss of less than $300?

Yes, you should enter the information from Schedule K-1, as the IRS receives a copy and will be expecting to see that loss on your individual tax return.

The easiest way to find any section of TurboTax is to open your return and use the Search box at the top right side of the TurboTax header. Click on the magnifying glass, type in the topic you need (ex: sch k-1), hit Enter, and click the "jump to" link to go directly to beginning of that topic.

Or go to Tax Tools >> Tools >> Topic Search. Type in your topic, then click the topic in the list to go directly to the start of that section.