This isn't the only way to resize - it's just my way
Decide on the pic you're going to upload from your computer to your image hoster and right click on it.
Click on Edit.
On the screen you'll now have the option to 'Change Picture Size' - resize or compress.
If you click on compress and then click on web pages when the screen changes the pic will auto resize to a window of 448x336 pixels. This will reduce the file size and speed up access to the thread.
If you click on resize (instead of 'compress') you get options of what new size you want.
To choice a new size click on 'Predefined widthxheight'.
Click on the box below and choose 'web large - 640x480 px'
or 'web small - 448x336'
Click ok
If you chose to resize you will now need to compress the file as described above. This will reduce the file size and speed up access to the thread.
Once you've got your resized pic you need to save it (I rename the new file & keep the original too!)
You've got the rest of it pretty sussed, so I wont keep blathering on
