You can chamfer edges in Blender using the Bevel Tool (from the Edge menu). To do this, enter Edit Mode and select one or more edges on your object. Hit CTRL+E to bring up the Edge Menu and select Bevel. Alternatively, hit CTRL+B to enter Bevel mode immediately.
Now move your mouse and the an edge being sliced off. Scroll the mouse wheel to add/remove more segments to the bevel, hence creating our desired chamfer effect. If you don’t have a mouse, you can use the plus and minus keys to add/remove segments to the bevel.
Left-click when you’re done.