Step by Step Tutorial on Adjusting the Brightness of a digital Image in Adobe PhotoShop.
Step 1:
Open the image in photoshop under the menu bar by selecting File and then Open.

Now the original image is opened and on the screen, ready to have the brightness adjusted.

Step 2:
On the menu bar under Image you will find adjustment and then under adjustment you will find the option brightness/contrast. Select brightness/contrast.
Then the following dialog box will appear
Step 3:
Slide the sliders in the positive direction to make the image brighter and have more contrast. If you desire the image to be darker or have less contrast then move the sliders the opposite direction. I moved the sliders for the leaves images as shown above and below is the result.
Step 4:
Now all that is left to do is to save the image. Select the File menu and then select Save.