Select your object and go to 'Effects' tab >> 'Movement effects' >> 'Section/zoom'. 'Movement' might not seem an obvious place to look but the effect is often made dynamic with key frame animation -- the 'Ken Burns' effect.
The area you want is selected by dragging the edges of the marquee in the preview window. If you have the 'Fill screen' box ticked you will get a zoom rather than a crop.
You didn't say what version of MEP you're using. For MEP 15 and later follow Carl's instructions. Before that it's a bit different. In MEP 14 for example you'd use Effects > Movement > Cam.movement > Cropping and movement and then choose from the drop-down list, e.g. Free Proportions.