I am having some trouble figuring out how to load photos from my computer, online, etc onto the forum so like generating a pet for a contest etc. Can anyone explain how to do this?

well, for sylestia pet images it's just a matter of getting the pet image url and sticking it between a set of [img] tags. (note [img] tags, not [*img=], which are for when you want the image to link through to something)

Same with other images from online.

Images from your computer you'll need to upload onto the internet using a host site (eg. Imgur, deviantart, phorobucket), but once you've done that... it's just a case of "get the image url and go"

There's at least one guide on how to get image urls in the Player Guides forum if you need help with that

Right-click on the pet you designed in generator, click 'copy image address', click on the blue IMG bow that appears above the text you type in a reply, click between the two sets of brackets that appear, ctrl/command+v.