Chopped Photos

I don't know any of the information required, however hopefully my problem is a simple one. I am loading photos into my band's website in your gallery program and they are getting chopped and some look very grainy and enpixelated (sp?)
I looked through the editing for both individual photo and album and need to know if there is a setting that will automatically size them to the window. There is an area where you can choose sizes and it is set to the default of 640 x 640. I am a total newbie to this. We used to have Version 1 and it worked great until we started getting error messages and had to upgrade.
I receive JPegs from a number of sources and need to now how to size them, whether manually or automatically to make them fully fit with best quality. I think I have Version 2.
Thanks in advance.