I haven't looked at your website but to reduce the size of pictures you just need to take them into a photo program and find something (usually under some menu along the top) that says "Image Size" or "resize image". Something like that. They all seem to be set up differently but if there are drop down lists and you have the option I suggest picking "inches" instead of working in "pixels", for me personally its easier anyway. And the programs I work with have an option that "constrains the porportion", thats critical as well. I have seen some though that don't have that option unfortunately. I like my pictures to be around 3in either height or width and then the program portionally adjust the other (height or width). I also watch the box that tells me how big the file is. Usually the pictures I use are 250KB or less. Alot of people say "oh they have to be under 100kb", I personally don't worry about that as much because I'm more worried about the size of the viewing area, how big the picture will be to the eye.
The resolution of the picture can also play a big part. If I have a picture that is 300dpi then I usually have to make the "size" of the picture 1 inch or smaller on either the height or width. My 3in standard of height or width is based on a common 72dpi picture.
Also I crop as much as I can on a picture BEFORE I ever readjust the size. I don't like a lot of extra grass and other background if the focus of the picture is suppose to be a horse or such.
Thats just how I do things...
I use PhotoShop to work on my pictures. I've also used ACDC Viewer I think it was called. And I've been told MS Paint can resize images, although it doesn't give enough options/info for me personally to resize the images the way I like.