Can you add images by html, instead of the uploader?

I posted another topic about image uploader problems, but this one is more about how to use images without it.

I was wondering if you can link to an image, like with an img tag in your post? If I upload the image to my site, say in a folder in my theme called “post pics.” Is there some way I can direct the link to grab that image? So the code would look something like:

<img src="www.myblog/theme/postpics">

That’s not the correct way to do it I’m sure, that’s why I’m asking. How do you figure out the directories where your images are stored so you can link to them?