Hi Arne, welcome to wetcanvas.
This is a terrific community and a wonderful resource, use the rolling menu bottom right and you will find forums for just about every art and craft medium here, it's worth exploring the full list of the forums. Read the posting rules at the top of the forums there may be restricted posting.
The links in the top line of my signature will help with the forum and how to resize and post your pictures. You can start uploading pictures on your third post.
A frequent question is "Where are my files?" When you get the uploader box and browse for your photos, make sure you select "All files" or you will not see your jpg files.
If you have a particular site problem, click on my name and send me a private message (pm).