On the Home tab Map Tools in Map you will see Magnify. 

This switches on a magnifying glass that you can rollover the map to zoom in on certain details quickly. This is especially useful with bigger maps where the objects start to look a little smaller.

Also in the bottom right corner of the Map there is a zoom scale that you can use to zoom in or out of details. Here the scale is set to 70% zoom.

Zoom in and use the preview box to move around the map, or zoom out to create extra space around your map on the canvas.