In the menu "World Puzzle Days" you can find all basic topics about the World Puzzle Days. To send your finished puzzle, simply choose the page "Send your Finished Puzzle" and fill out the submission form. 😉
Note! The form will not take photos of more than 2 MB! In case your cam creates too heavy photos, there is a very simple way of solution. Upload all your photos to your personal album. (You would do this anyway with all other photos of progress. But upload also the photo of your finished puzzle to this album!) Then open it on facebook and save it again on your computer/tablet/phone. Facebook compresses all our photos automatically to ~600kb. After downloading your own photo, it should be accepted also by the submission form to send your puzzle to Günther.
You can do the same trick also by facebooks "Messenger", sending your photo to yourself as a message and downloading it again from there.
So you will not need a programm like Photoshop or a special website to compress your photos. 😊