Follow the step-by-step instructions that come with Shimano mechs (they're on the Shimano website if you haven't got them) and you shouldn't have any problems. Just follow the steps and you should have super sweet shifting, it's all pretty straightforward stuff.
If you can suspend a horizontal bar/plank/pipe etc between two posts/fences/trees/tables/chairs etc and hook the nose of your saddle over it (lower your saddle all the way if you need to) it should work as a makeshift workstand to get your rear wheel off the ground and allow you to rotate the cranks and rear wheel.
Enjoy finishing the build, it's always a really satisfying time.
Oh, and the one thing you will need to get your drivetrain really fettled properly, a beer (go on, make it two). A very chilled way to spend an evening I think.