With DPP, make sure the tool palette is open and then click on the image you want to crop and use your mouse to select the rectangular outline that you want. You can set DPP to crop to a specific aspect ratio, for general editing I paste a recipe to my RAW files before editing and setting cropping aspect ratio to "free" is one part of the recipe.
In the attached image, the tool palette is open on my second monitor with the crop tool selected (second symbol from left on top row of tool palette. Once you select the crop, you can switch back to the primary edit tool menu (second row of tool palette, farthest left) to do exposure, color, sharpness etc. adjustments and the image showing in the edit window will be the cropped photo. (Second attached image).
Rodger
