Can't copy-paste: Newcomers usually copy and paste more. So don't copy someone's post or text from any website. Copying and posting is a big injustice. If someone regularly copies and pastes and gets caught, you can get a much bigger penalty.
It is possible to copy and paste a content, just don't copy the whole of the content and when you done with it you have to included the link of the source or where you get that topic or content. I have done it before where I copy some of it and add my own understanding then provide the link of the site where you copy. It won't be considered as plagiarism since you did not post it as your own. Just make sure you include the source or else it will be a plagiarism.