Though you can resize images in webpage composer programs, it is good to resize digital images before you insert them into a webpage so that the files are no bigger than they need to be.
 

1. Open Adobe Photoshop
2. Select File > Open > File
3. In Photoshop, select Image > Image Size to adjust image size.
4. Choose File > Save and save as a .jpg file.

Other commonly used tools in Photoshop:

Anything you are doing will only happen in the selected layer.

Remember, you must choose Layer>Flatten Image and save as a jpg or gif file to use this on the web.