So ive seen some comments that have a picture and some text with it how do you add the picture?

You just put "thumb #" along with the ID of an existing post. So if you put

thumb #291429

you'll get post #291429

The ID is located in your addressbar or at the Statistics section (left side after the list of tags) when viewing a post

Also, you can make custom hotlinks to outside pages or images like so:

"text of choice":URL

"See? Like that.":http://www.rowsdowr.com/wp-content/uploads/2012/09/Vxzhkh.jpg

See? Like that.

And E621 posts can also be hotlinked to without showing a thumbnail by using:

post #number

So like this: post #493722

That one's particularly useful when you're filing an image for deletion and need to refer to a duplicate or something like that.