Posting an image in HTML is actually really easy and hopefully this tutorial will help to simplify it somewhat.
First of all, an image needs to be uploaded to the web in order for you to encode it elsewhere on the web. Most of the time, this means you'll have to upload it to either your own photobucket account or to myspace or another image hosting site. But if you see an image on the web, you can usually post it somewhere else without having to upload it to your own account.
Some sites put in measures to prevent what is known as "hotlinking." I must stress also that hotlinking is rather bad form because it's using someone else's
bandwidth, but debate on this gets a little convoluted for beginners. So for now we'll just assume you've seen a picture on a friend's myspace page and asked if you can use it.
Now, how do you do that?
It's simple really.
First use your mouse and right click on the image you want to use.
You'll see something like this:

Each browser is different, but what we want is the "properties." That is the image location, the size and sometimes even the author!
When you click properties you'll get something like this:

Again, not all browsers will look like this, but all you really want is that URL there. Right click on the URL and Copy it.
Next, we go back to the page where we want to post it. And here is where we write in our tag:

The black text is the actual tag itself. The red text is where your URL will go. so basically there will be nothing between those quotation marks till you right click and paste the URL of your image like so

I've used the blog window here and the result is this:

Say we wanted to do the same thing, but with an image we've uploaded to photobucket...
All you gotta do is use that same tag:

And in between the quotation marks, place the direct url:

The others around it are pre-made tags that, if all has gone well here today, you probably won't need to use.
Now, we can get into some
fancy stuff!
Lets say that you wanted to put an image in your profile, but it's too big and you want it to fit nicely. You can resize the image without having to go into photoshop or opening any graphics programs with a little html.

If you wanted to keep the original proportions and do even less coding, you only need to specify either the width or the height! It'll resize the image to what ever size you want like so:

I only specified the width to be 450 pixels in the image above. You can use whatever numbers you want. One could of course make the image really short and wide. like so:

Of course, that looks a little weird. But hey, that much is up to you to decide. Depending on the image, it might look better like that.
The last thing I'm going to teach you today is something rather neat! Of course, I'm the sort of person that likes to read the street and store signs in the Simpsons, or find easter eggs in DVDs...So the 'alt' tag was fun to learn and something I miss since migrating to opera. There's a different tag that should work on opera but I've not learned it yet. Regardless, 'alt' stands for alternative text. It is the text you'll see if you have images turned off in your browser. But in
some browsers, it will also roll down in a little box beside the mouse when your mouse hovers over the image. This is what's known as a "mouse over."
Anyhow since I'm not psychic and I can't tell which browsers you're using, I can't tell whether you'll be able to see the effects in here. But I can show you how to do it! And if you're using Internet Explorer you
should be able to see it.

All you need to do is add the green text in, and put whatever text you like between those green quotation marks. You don't need the width and height tags, but I thought I'd include them to show you how to do the full thing.

Place your Cursor over the hamburger and don't move it for a couple seconds...
Neat huh?
Now remember, this is the sort of thing that will get much easier the more you practice. You can practice in the comments here if you like and you can even use any of the images I've posted in this blog. You can save the pics of the tags too if it helps.
I didn't have as much time as I would have liked to spend on this blog, so if you have any questions, please don't hesitate to ask them here or in mail. Remember, it's nothing to be embarassed about. The only stupid question is the question unasked!
In the next tutorial, I'll be covering hyperlinks. Hopefully you'll join me then too :)