Resizing images in Photoshop
You don't necessarily have to crop an image to resize it. That's just an added plus if you were planning on cropping the image anyway. If you wish to resize your image without cropping, Photoshop offers a number of methods. This tutorial will show two methods, one here, and the other method when saving your photo at a later section.
Click on the image menu. The image resize option will be found under here.
Once open, the image resize dialogue box will display. This box will present lots of options for a variety of purposes.
Notice that there are two sections to this dialogue, the Pixel Dimensions section at the top and the Document Size at the bottom. When working purely for the Web, you can completely ignore the document size, since that is only for working with media that will be printed on a printer.
With the pixel dimensions section, you simply type in the values of the height and width. If the Constrain Proportions checkbox is checked, then when you change either the height and width the other value will change respectively based on the ratio of their dimensions. You should always leave the Constrain Proportions checked or else you will distort the photograph.
If for some reason, you cannot edit the Pixel Dimensions, that means the Resample Image is not checked. Resampling the image is a fancy way for saying that you can change the size.
To follow along, change the width to 600 px. The height will automatically change depending on the ratio of the image.