Readin', 'ritin', 'rithmetic. But seriously, huzzah on joining the writing masses.
Obvious first up, is you want an idea, a story that you can tell. Then, you want to get to grips with the framework - as in, how to go from outisde the house, to checking each of the rooms inside, to the big scene in one room, and the links and variables that'll do that for you.
And you'll want to keep yourself interested, and motivated, and have some friends look over it and test it for you. There's a lot of fantastic articles on the Help & Info page, that'll get you started.
But huzzah again!