You can resize from Image->Resize->Image Size. Click on resample to change the width and height. usually for web most of the folks use save for web feature which is what will suit to you also. Here is the help link for save for web http://helpx.adobe.com/photoshop-elements/getting-started/save-web-friendly-format.html
Please open the file in PSE Editor and do File >> Save for Web.
You can get more information on image resizing from the link below-
"To resize a photo for the web, choose File > Save for Web. Choose your file format, choose a color profile, and type in the pixel dimensions you need. Click Apply, and then compare the original photo to the compressed version to ensure that you're satisfied with the resulting quality." quoted from <http://www.adobe.com/in/products/photoshop-elements/image-resizer-resizing-pictures.html>