Boujohn, when you attach images to an entry, you can change their dimensions (width, height):
You can also change the default image settings in the module settings (Control Panel -> the module you need, e.g. Site News -> Module settings:
The answer you reference appears to be for modules such as News or Blog ... my issue is with web page editing:
There appears to be no sizing fields next to the image upload control ... nor is there are there image size attributes on the Common Settings page (for page editing there is no Module Settings panel).