If you have an account with photobox, picassa or similar its easier to upload them to there and then link to them. If not I'd sggest getting one - they are a great way to store and share your photos and videos across lots of different formats.
Personally I use Picassa which is from google and offers massie storage space for free.
It might be best not to upload stuff to this sites storage at the moment as the forum is going to migrate to different software shortly but if you do you need to resize your photos in line with the details given in the Gallery which can be found from the homepage.