You can highlight other people's work in your posts, but not copy it. Any time you reference someone else's original content, cite the source. It's not all that different than writing a paper for school, and there's nothing wrong with incorporating cited sources that support what you're blogging about. It takes a minute, but once you break the "retweet" and "share on Facebook" habits we've all gotten accustomed to, you'll do fine. Oh, and welcome to Steemit!