It's not too hard once you know how.
Any one file can't be larger that 1 Mb.
You're only allowed a total of 2 Mb/post.
Use your photo editor of choice to compress pics to a size relevant to the detail you
need to show. 100 KB is usually heaps enough detail.
Add them individually into the 'Attachments" UI below this posting box but take note of the file types allowed.
Then they're displayed as thumbnails that you can copy their URLs and place between in [ img ]image[ /img ] tags available from the Insert Image icon.
Sometimes for a few images it's easier to open dual tabs, editing one with URLs copied from the other.