There is a few different ways to post pics....
you can go to
http://imageshack.us/ or
http://photobucket.com/
create a account there and host you picture for free...then you can link the pics to the post you have
or as a supporting member ($10 a year) you are able to insert the picture in your message (like above) and it is hosted on the Waltherforum.
Seeing that you are a member what you can do now is go to your WTS post and edit it or just reply to it and then attach the pics.....
When your at the box your writing your reply in..... scroll down a bit.....it will say attach files.... click "manage attachments" then choose the picture you want to attach
and it should all work out