There are several ways, depending on exactly what you want to do.
The most obvious is
If you are specifically looking for best way in PSE to resize images for web etc save for web solves your issue. http://helpx.adobe.com/photoshop-elements/getting-started/save-web-fri endly-format.html
There is Optimize to file size text box in whcih you can enter your desired size and sit back. When shown done click ok and save and you are good to go.
Quick, easy to use though powerful.