You can add both featured and insert images into your posts or pages.
Add these with the post (or page) settings on the right side of the post. These will typically appear above or below the headline, often in a shape/format that links to the theme design.
Add these to your post (or page) by clicking the plus mark to add content in the text editor box. Once added you can click the photo to resize it or to change its alignment. Galleries are added just like a single image. The only difference is you select more than one and choose a gallery style.
In both cases, you add captions when you insert or you can edit them after placement to add or update captions.
Table of Contents:
00:24 – Add featured
01:03 – Edit to add caption and alt text
01:20 – Where your featured image appears
01:32 – Insert
02:01 – Resize and change text wrap
02:29 – Insert a gallery