K-1s are used to report income and expenses from pass-through entities to your personal return. When you receive a K-1, there should be an instruction sheet or supplemental page that will generally show you where each box on the K-1 is reported on your Form 1040. That is a place to start.
You might want to consider purchasing the 2018 TurboTax program and re-creating your 2018 return exactly as it was filed. Complete the 'filing' process by choosing to file the return by mail. Then, you can use the program to generate your amended return to include the K-1s. It may be easier than trying to create Form 1040X by hand.
Also, you mentioned that you are amending to include the K-1s for you and a family member you claimed as a dependent. If you meant that one of the K-1s was issued to the dependent shown on your return, then you should not include that K-1 as part of your return. The dependent may need to file their own return to report the K-1 information.
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