You need to find Obi-wan's ghost, and he'll give you The Force. He's somewhere in each world. If you have the locator (if you don't, find it, it should be in one of the map squares near the spaceport), the map square where he's located will have the label "Find the Force" or something like that.
So what your saying is find the locator first and then find Obi-Wan? because Luke keeps saying I sence a disturbnce in the force
just use the process of elimination. Go into every square until you find it. There will be squares that you just need to walk through, squares with puzzles in, a square with the main puzzle in, and the spaceport, if i remember rightly. It won't take long to wander round the whole map. But yeah, find the locator, which is in one of the 8 squares surrounding the spaceport, and you'll be able to see the map. After completing 5 games, I think, you get the green lightsaber, after 10, you always start with the Force, I think, and after 15 you get a Spirit Heart, which I think means you can die but carry on...
You don't have to find the locator first, but it helps. And if Luke starts talking about the Force, you're probably in the right spot. Usually you have to solve a simple puzzle to get to Obi-wan, though. Like push some blocks into the right places, hit a button, mess with some trees, clear some snow, etc.
now i want to play yoda stories Seriously some of those hordes of stormtroopers in the later levels got pretty insane.