Images, formatting and links all work through something called Markdown in Steem posts and comments. I just uploaded a post about it actually so you may want to take a look at that.

If you want to post photos you'll need to upload them online so they can be hosted and you can get a link to them. I've had problems with imgur and Steem so I'm using Imgsafe, there are other options too though.

(2) I'm not sure about but the fields to enter data into when posting are:

• Tags - this is the section you want to post into, for example you posted this into steemhelp. If you want to enter multiple tags separate them with spaces.
• Title / Summary - these are the bits that get displayed on the link to your post in the list of new posts etc
• Reply - here's where you can dump the content of your post and its markdown (see my post above).