How to add new content to your blog:
1) login to backend as manager
2) look for the top vertical menu and direct your cursor to hover over "Content"
3) follow Content by Section > My Blog > My Blog Items
4) click on My Blog Items
5) at the top right you'll see some faded grey icons - click "New"
6) add your new content
7) add title, title alias, and pick category "My Blog"
8) on the right, you can remove the checkmark from the published box if you prefer to save as a draft
9) when you're ready to share your writing with the public check that same box
10) up to the grey icons again, click "Apply" to save while continuing to work, or
11) click "Save" to save and exit
12) you're done!
If you want to add images, you need to upload them to the site. That's another fairly easy step-by-step process I'd be glad to explain.