Christine, you should not be sad, you are on your way towards real good pictures. Always keep the out of the camera original secure, so that you can go back and start over. In a couple of years may be you have learnt more og there are better tools to work on it again.
Regarding the size of picture, there are to different sizes. The first is the pixel size limit that different web sites impose on you. In Birdforum there are several different limits. In the Critique forum you have to limit your picture to 640x480 pixels, in the Gallery you can upload picture size 800x800 pixels. The other size limit is the file size limit. In the gallery the size limit is 250 kb, in the critique forum no limit are mentioned, but I think probably the same. You must use the JPG format, which compress the file by chunking together block of pixels, thereby degrading the picture quality, if compressing to much. When you save as JPG, you have to opportunity to choose the degree of compression. It should be indicated how big the resulting file will be. Some programs let you "Save for web" and give you 2 to 4 picture with different compression to compare. It should not be evident that the picture is compressed.
You must keep the camera setting that you have, you need big files to keep the quality of the picture for viewing on screen and for printing on paper. Myself I convert the JPG made by the camera to TIF, because I don't want the file to be degraded when doing postprocessing with several saves. A JPG file will be more and more chunky if you do so. The back side of that is that the files gets very big and demands much hard disc space.
All digiscopers take hundreds of pictures to get a few good ones, so keep the spirit up, and go out and take some more.