No worries, upload all the pictures you want to use to photobucket. Once there copy the IMG code and paste that code in to you post. It will appear as a long line of code in you text box but as a picture once posted.
Other bods I know use photobucket (?) or something similar, basically all the same but you have to pay for using.
Once you have your images on Smugmug or Photobucket you can upload onto your forum reply by clicking on the 'insert image' button just above the smiley's.