All you have to do is finish the building. Sound easy? Then you're forgetting about certain government regulations, the neighborhood punks, and the fact that falling bodies (including your own) accelerate at the rate of 32 feet per second/per second. It's a tough life, maybe. But it makes your beer taste better.
Along the way, you'll want to grab all the bonus items you can get to. They're worth points.
Jumping off any level onto the springboard will vault you to the next highest floor. From the top, you can springboard to the ground floor. You can also change floors by scrabling up and down the chains, or by riding the elevator. From the top girder you can ring the bell to bring the elevator up. Your enemies are OSHA, the Vandals, gravity and time. The quicker you finish the steelwork, the higher your bonus points will be.
A Word of Advice - First level isn't easy. In fact, it can be pretty challenging the first times you play it. So use your wits. Check out the patterns of the stuff that can wipe you out. Try to be conservative at first. Speed will come with skill.
Time your leaps onto the upper floors carefully and get all the bonus items you can while you're collecting the tool boxes.
Finish the level by timing your ride up the top floor conveyor so the big magnet will pick you up.
The twin springboards at the bottom will help you to cross the abyss.
Beware of the port-a-potti. Look out for the exposed wiring near the conveyor belt. Don't fall into the rivet machines.
Avoid all these things and you will gain enlightenment and the opportunity to be Construction Kingpin in the great metropolis of the future.
You'll also gain the opportunity to go on to level 4. And level 5. And level 6. After that, the sky's the limit.
Now put it in gear and get to work.