Sometimes the Bitmap is just too large and you need only a part of it. Then you use Crop to Object tool.
The trick is you place or draw a rectangle object over the part you want to keep. Select both the rectangle and the Bitmap (by SHIFT clicking or dragging a selection rectangle around them) and from menu Bitmap select Crop To Object. Now you will get the Bitmap object in the size of the rectangle.

Tip: You can use different shapes instead of rectangle to get an interesting effects.