Hello once again Horst!!
Unfortunately it is not possible to upload a photo to the website servers. The picture must already be online on some kind of photo sharing website like Flickr.
Once the image is uploaded you can then link to it from the photo sharing site so that it displays on here. To learn how to do this have a look at this post by forum moderator Thomas
or this entry in the FAQ section
of the website.
The forum guidelines are that the images you post must be no larger than 1024 pixels on their longest dimension. The exception is the On Assignment section in which pictures should have a max longest dimension of 500 px.