Krisakira seems to have a newer Photoshop than mine (and an Apple-flavored one besides). The appearance is different but the questions themselves are quite familiar.

When I go to save a file after resizing the image, I prefer to use the "Save as..." function. That way I can save the new version as a copy instead of overwriting the original. If I don't like the result for some reason, I might want to go back to the first version and try again.

Photoshop may ask you what to save it as. It usually works best to stay with the same file type as the original (.jpg, .gif, etc.) Don't choose .psd for an image you're planning to upload to a website because only Photoshop can read that.

If you're saving your image as a .jpg file, Photoshop will probably ask you what quality level (1 to 10) you want to save it as. The higher the quality the larger the file size, and my Photoshop (at least) doesn't tell me ahead of time what file size to expect. For an avatar I'd probably start with medium quality, around a 5. If the filesize turned out to be too big (over 29.3 KB), I'd go back and try saving as a 4, a 3, or whatever it took. If you have to go that route, do go back to the original each time. Each time you reopen and re-save a .jpg, you lose some information and picture quality.

If you're saving your image as a .gif file, Photoshop will ask you a completely different set of questions. I don't know the best answers to any of them but accepting the defaults usually works for me.

Good luck, Sabrina! It's actually quite easy once you get past the initial unfamiliarity.