To sample a color from an image in Photoshop, start by opening the image you want to work with. Once your image is open, select the Eyedropper tool by either pressing the 'I' key on your keyboard or choosing it from the toolbar where it's often found alongside the Color Sampler tool. Click on the specific area of the image where you want to sample a color. This action automatically sets the sampled color as the foreground color in the color picker. To view the sampled color, check the Foreground Color swatch located at the bottom of the toolbar. This quick and straightforward process allows you to easily capture and use colors from your image within Photoshop.