In this tutorial you will learn the basics of image manipulating techniques. These techniques will be useful for customizing scanned images and images taken from other sources like the web for use in a variety of applications. ...

Almost everything you need for basic Photo- shop image manipulation can be found under the Image menu.
It allows you to modify many attributes of the image.
You can make fine or coarse adjustments and create a usable image using not much more than what is found in this window.

Though your image is mostly upright, it still is slightly skewed to the right.
You can rotate it that small amount to the left while at the same time cropping all the excess you donâ t want, out of the picture with the crop tool.
To select the crop tool, either press the C key on the key board or click the crop tool on the tool bar and it will turn white to show that it is selected.
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Source: media.uwb.edu