Petra:
The best way is simply to put your butt on your bike and go ride, girl... ;-)
Find a big empty parking lot and ride in circles, figure-8s, whatever, and learn to be comfortable and confident handling and controlling your bike... starting, stopping, clipping in and out, taking corners and making those nice swooping turns at speed, riding slow and track standing to improve your balance, etc.
Find a quiet section of path or a queit neighborhood, and ride at a selected pace to build your endurance, so tht your "motor" will take your bike and you whereever it is you want to go, and still have energy to have fun (and still get home) when you get there.
Once you have a little endurance, put a little more effort out, for example by doing some simple intervals, sprints, and hill climbs to build your power. Power makes you faster, lets you go up hills, and lets you run down and catch that cute feller on the Trek way up to road just to show you can drop him like a cold 'tater ;-)
A website and weekly newsletter that I've found useful has been http://www.roadbikerider.com, which features a number of good E-books on cycling, the aforementioned weekly newsletter, reprints from old newsletters, and bunches of other stuff. The forums here at TE offer a whole lot of good advice, as do the forums over at www.bicycling.com.
There's lot's of cycling books out there, but few of them will do you any good without a good bit of time in the saddle figuring out what advice works for you. Experience is the best teacher, it's just that the tuition is so derned high ;-)
Happy trails...
TE