I am posting this in response to a question I received in the comments section earlier about posting pictures.  Unfortunately, the comments box does not allow me to demonstrate what I am trying to explain.

When you create a new post, there is an icon at the top of the dialog box that is the insert media tool (in red).   I hope this is helpful.

Clicking the Add media button opens a new window what you can images. Below the “drop files” box, is a set of formatting options. Captions (like this) are entered in the “caption” box.