Hello & Welcome to the club mate.
The red button is to take the car out of P (Park) when the car is turned off (or you have a flat battery)
The lights on the dash tell you what gear you're in, P = Park, N = Neutral, R = Reverse, D = Drive.
The Manu button is to drive the car manually. L = 1st, 2 = 2nd, D = 3rd & 4th.
You'll no doubt discover the O/D (overdrive) button too. With 'O/D Off' you have no 4th gear. The O/D button is good for when you're tootling along in 4th and you wanna overtake. Turn O/D off and you'll change down a gear to 3rd before you overtake. This avoids having to engage a 'kickdown' during a takeover maneuver.
Hope that helps dude!
BTW, what car you got? TT or N/A. Oh yeah, wheres the pics?