It depends on your niche.
If you are doing a step-by-step breakdown of a process, getting pictures is pretty straightforward.
You can just do screenshots using Lightbox or any other tool to lend credibility to your posts.
Remember, the whole point of adding pictures to your posts is not to make them pretty. Your objective should be to clarify the ideas that you're trying to get across.
If you're able to do that, then your posts will be more valuable.
You don't have to necessarily use copyrighted pictures.
You can just use stuff based on the operations or steps you're going through.
But if you're reviewing a product for example under the copyright fair use jurisprudence, you can use otherwise copyrighted images like logos and companies' product pictures for the sake of making a review, doing some sort of commentary, or publishing news about that item or brand.