The system should automatically shrink uploaded photos down to a smaller size, which can then be expanded to full size by clicking on the browser.
More likely, you are trying to upload photos that are too large in terms of the size of the file, not the image itself. Try reducing filesize. if you have a PC, you can use a program like Paint Shop Pro, or if you have a Mac, you can use something like GraphicConverter (my program of choice for about 15 years).
Cheers,
Gerry