Activate Developer mode by right clicking in BVE 4.2 and click "Options", then in the tabs on top press "User" and click "Developer", then press "Ok". After that right click again and press Viewer mode/ctrl + m. Deactivate Num Lock, in the numpad (the one beside enter not ontop of the letters), press 8 and 2 for moving upwards and downwards, 4 and 6 for left and right and front arrow and back arrow for forward and backward. Well you can also drag with your mouse too.