You explained it very well.
Add this remark at the end of your achievement if you got all concepts of plagiarism. It was in the guideline provided by cryptokannon

please put remarks,
"I have read and understood the Steemit Etiquette on Steemit Community and will do my best to embrace them" at the end of this task post.

And the same way, if you are quoting someone line or some saying you can do with the help of this symbol ">". Place this symbol and paste the sentence. As you can see I have done below. It will appear like this.

quoted sentence

For more details, you can read cryptokannon guide for achievement 3 from here Achievement 3 : Content Etiquette

Hope so you'll be enjoying your new journey here on steemit.
Happy steeming )