you are missing "function main" which must be in all main scripts, while you can include other scripts in your project you must have one main script that starts every thing.
////////////////////////////////////////////////////////////////////
#include <acknex.h>
#include <default.c>

function main()
{
video_screen =1; // set fullscreen mode
video_mode =8; // create a program window of 800x600 pixels
level_load("YOUR_LEVEL_NAME_HERE.wmb"); // loads the level you name here..
wait(-2);
}
function move_up(Square)
{
while (!key_w)
{
my.z+=1*time_step;
}