Need some beginner help with [img] tags (Probably an easy question)

Heya! I’m trying to get some pictures of different sizes to all display as one size, or at the very least scaling down the larger images. I’m familiar with how to display an image but not on how to resize it. If that’s even possible (which it might not be). If it is, I really need to learn for an album art thread I’m trying to throw together, so thanks a ton for any help anyone can provide 😀 😀 😀

Use this:

*You may omit that part of the code.
Replace "[" and "]" with "<" and ">", respectively. Also, replace 640 and 480 with the desired values. It’s a HTML code.

EDIT:
The best option would be for you to resize the image locally, through a software like GIMP or Photoshop, and later host the resized version. Think of this: you have an image like – 1400×2000, 891 KB. You may shrink it through a code, but both you and other users would still load the [I]huge 891 KB file.

Thanks a ton for all the detail, I really appreciate it!