Wrong Section. Anyway, here's how.
When posting, go to advanced posting (The one with all the features and stuff). Scroll down slightly and there is a button that says manage attachments. Click that and upload the file from your computer.
You now have two options:
1) Click the paper clip icon on the bar with all those stuff. Then, simply click the attached image to insert it.
2) Right click on the attachment. Click properties. Copy the URL and put it in the field of "Insert Image". This way is preferred as the image will not be shrinked/scaled.
Hope this helps.
