The easiest way I've found to do it is to use a Photobucket account. It's free to sign up, and it's relatively easy to upload the pics.
Once you do that,
1. In your post, click the icon that looks like a "tree with a frame around it". That will open a dialog box that says "Please enter the URL of your image"
2. In another browser tab/window, go to your Photobuck account
3. Upload your picture to Photobucket or if already uploaded, Select the picture you want to post
4. You'll see a field called "Direct Link" with text in it that looks like an internet address...it is. Copy that text in its entirety.
5. Go back to the tab/window with the "Please enter the URL of your image" dialog box.
6. Paste the text string you copied from Photobucket.
And you should be done...
If anyone knows an easier way to get this done...
And if any of that isn't clear, just let me know...
Charles