There are several sites that offer royalty free photos. Unsplash, Pixabay, and Pexels are the ones I use. (you could always do a Google search for free photos or royalty free photos to find sites.) Sometimes I upload my own photos.

I download the free pic onto my desktop and copy the person's credit info.

This may be redundant and I hope not insulting:

When you press the enter or return button in the context of the article you're writing there's a number of icons: one in the shape of a camera. Click on it camera, then it will upload the photo into your piece. Then I paste the person's name and info into the caption below the photo.