You cannot copy your photos directly into most forum websites (eg, TRS). Textual words are small. Photos are huge, so they consume too much storage space ($$$).
So, you've gotta join a photo-sharing website (eg, photobucket.com, flikr.com, imgur.com, skydrive.com, etc.). There are so many, and most have freebie offerings (see
http://en.wikipedia.org/wiki/List_of_photo_sharing_websites ).
Then upload your photo from your computer, up to that internet photo-sharing website. That makes your photo exist someplace on the internet, so then you can get its URL (ie, universal internet location) of that specific photo. A URL looks like "http://whatever.jpg"
When posting into TRS (or any forum), you click the yellow icon that Rangurr mentioned. That icon asks you to "paste" a copy of your photo's specific URL into the box. Presto! Your TRS posting will display the photo, even though the actual photo lives out on the internet, outside of TRS itself.
This allows TRS to refer to your photo without paying extra $$$ to store copies of your photo. Also, each photo-sharing web site usually gives you choices about who is permitted to view each 1 of your photos, in case you want some to be more private than others.
Got it?
Step 1: join some photo-sharing website
Step 2: upload photo to that website
Step 3: get a copy of its URL (ie, its address)
Step 4: paste its URL into your TRS post