To post pictures, all you need to do is put in a link to the
picture if it's already out there on the internet. For
instance,

will
be replaced by the Democratic Underground logo from the home
page.
To get the link to the picture, all you need to do is
right-click on the picture and choose 'Copy Image Location'
in Firefox and then just paste it into your post or for
Internet Explorer you need to right-click on the picture and
choose 'Properties' and then you'll see the location of the
picture in the window that pops up. You can select and copy
it and then just paste it into your post.
If you want to post pictures that you have on your hard drive
you need to get a free image hosting account at someplace like
http://www.photobucket.comWhen you upload your photos to photobucket, they'll give you
the link to use in your posts.
Hyperlinks are really easy. Just paste the link to the page
you want into your post. DU will make it a hyperlink
automatically.
If you want to get fancy, or do other stuff with HTML, then
click on the 'HTML lookup table' link when you create a new
post.