Welcome Peter.
Uploading pictures can be infuriating. You can use a Hosting site. I use Imageshack, where on the browse and upload window, you can set the size to a suitable one. I use 800x600 that gives you a good viewing size without the need to scroll. They have a limit to how many images you can host on there, and can buy more space on a monthly basis.
Take is step by step and do not fret.