I’m unsure if it’s allowed to paste pictures I found from a local online newspaper if I credit them. It’s only a blog, but I’m looking to write articles and other writing projects, so I’d like to know what the legality of it is. Thank you!

Simple answer: No.

All "creative work" such as pictures, music, written works etc is automatically copyright of the creator. You are not allowed to make use of it in any way without explicit permission, called a license, from the owner. It is often a condition of such a license that the owner is credited, but crediting work does not rectify any breach.

There are some minor exceptions for "fair use". EG, if you are reviewing a book or film it is fair to include small excerpts or a still. But it would not be acceptable to use someone’s picture just to illustrate your own article.

Of course, people do this sort of thing all the time, and in the vast majority of cases nothing happens. But you need to be aware that what you are doing is technically wrong, and if you tread on the wrong toes you could end up in court.