You can use the built-in image editor to scale and crop photos after you have uploaded them to the media library.
Crop an Image
To begin, click on Media Library, then click on the image you would like to edit.
Below your photo, click Edit Image.
To crop the image, begin by clicking and dragging on the photo to create a box. The box will determine how the photo is cropped. Then, click the crop icon. (See below)
Scale an Image
To scale an image, first click Edit Image as shown above in the first image.
Click the Scale Image link to the right of the image.
Enter your new height OR width in. The other number will adjust automatically.