Changing Colour, Background, and General Settings

On the top toolbar, click "Preferences" then "Colours":

A colours window should appear. Checkmark the "Grid" option:

Now click "Apply", then click "Ok".

On the top toolbar, click "Preferences" then "Options".

A general options window should appear. Under "Units", checkmark the "millimetres" option:

Now click "Ok".

Zooming, Moving, and Redrawing the View

Scroll the mousewheel to zoom in and out. Alternatively, you can use the "Zoom In" and "Zoom Out" buttons on the top symbol toolbar:

Scroll the horizontal and vertical scrollbars to move the view left and right, up and down.

On the top symbol toolbar, click the "Redraw View" button to refresh the view.