if you have made a mod go to mediafire.com and upload the source and any compiled versions you have in an archive [I suggest zip because it is common] to make a mod, go to github and download the latest source and edit it. you can post a mod even if it only has 1 or 2 elements, this says that you want to help the development of Powder Toy but are just starting. you will get better as you go along. you do not need to know C or C++, although i hear that is helpful. I dont know C++ but have a mod. once you have uploaded the files to mediafire get the download links and put them in a topic under PowderToy Mods.
if you ever need any help [eg. updating the source, adding elements] just start a convo with me or go on IRC. someone will be able to help you.