How do you resize pictures?

When I try to edit my pictures on my computer it just crops the picture...but I want everything on there I just want it smaller bc when I go to upload them it says its to big..

use the program IRFANVIEW - freeware.
(most download sites have it, I prefer filehippo.com)
when you open then save the image (with a new name so you do not overwrite the high quality original) use the filters - check mark box for size - either smaller to fit on a screen or smaller bit size - like 60 to 100K size to make it a small email attachment either before or after you shrink the display size. Make sure you save as JPG, that is one of the best compressed size types.
(Some cell phones will only display .pdf instead of .jpg unless they are set up for it, if going in attachments.)
Experiment with the sizes, you can also crop out unneeded portions, lighten, flip, etc.