Hello Delphine -- welcome to the Forums!
In the tabs at the very top of the page, click to open "photos." On the blue menu bar, open "Gallery." Both take you to the same place. If you want to find them again I'd recommend posting in the Member's Photos category. When you go there, click 'Upload' between the blue menu bar and alphabetical row.
I'd recommend resizing to between 600x800 to 900x1200 pixels for best viewability and not using up your allotted storage space too fast.
Post back here if you need help.