The easiest way is to go to a hosting site such as www.tinypic.com.
Once you get there, you'll see the options such as "Tags" - title your photo and Size - choose message board.
Click "Upload Photo".
Once you have the photo uploaded, you'll see several options:
Links to Share
HTML for Websites
IMG Code for Forums & Message Boards
URL for E-Mail & IM
Direct Link for Layouts
Send it Via E-Mail
Click on the IMG Code for Forums & Message Boards .
It will be something such as (only without the spaces. I had to space it so the info would show up and not the image, LOL)
Then, just copy and past it in your post and the picture will show up rather than the small attachment version that you have to click on to view.