Soon, personally I find uploading the photo direct onto the forum is simpler.
Anyway, in order to get the photo to show directly in the thread, you need use this icon

.
First you copy the link to the photo, if you are using photobucket its the link under
Direct Link - Layout Pages.
Next you click the

button, a pop-up box will come out, make sure you delete the default http:// first, only then paste the link. Otherwise you'd end up with double http:// & the photo might not show properly.
When you press OK, the photo should display in your thread.
p/s: if you uploaded your photo onto Petpitcher page, the link to the photo is the one under Picture URL - when you click on the photo, the link appear below the photo.