Be it User Stories or Resellers, Support or Solutions, News or Blogs... these articles or posts are called Entries.
Creating a new entry is as simple as going to the Entries section and clicking on the + New Entry button. You can click the down arrow on that button to select the appropriate section for your new entry to live in.
The body fields splits up images, header text, text, quotes and embeds. You can add each item using the buttons at the bottom of the Body field.
Body items can be dragged and dropped, removed, enabled/disabled using the 4 dots or gear on the top right of each element's box.
Most entries have 3 tabs: Content, Meta Data, and SEO. The bulk of your work will be done on the Content tab. But categories and tags can be adjusted on the Meta Data tab.
The SEO tab can be ignored unless you want to make SEO changes for that specific page.
If you want to add a whole bunch of images at once, you can select Assets on the sidebar. Select an appropriate folder, then click the Upload Files button in the top right corner.
To add an image as a Primary Image, simply click on Primary Image and it will allow you to select or upload a new image.
To add an image to the body of an entry, this should be done in the body field.