When uploading or choosing images for your pages and posts, the image can be cropped from within the media chooser.
Select the desired image and click the “Edit Image” link on the right hand side of the screen.
In the Edit Image popup, click and drag over the image to select the part you want to keep. You can click and drag on all sides and corners of the selection to fine tune it.
When you’re happy with your selection, click the “Crop” button above the image, then click “Save”. The cropped image is now available to add to your content.