Don't listen to him.
![Wink ;)](https://modarchive.org/forums/Smileys/classic/wink.gif)
To each his own. Of course you can use the Draw button, that's why it's there. At first I thought you meant you couldn't figure out how to depress a sticky button (it's just another click) but then I realized what you probably meant: The Draw button (as well as the majority of the buttons) is unavailable when there's no sample data you can process. What you need to do is first create a blank sample and then you can get to modifying it, by drawing for example.
So:
1. Open the sample editor context menu (right-click, cmd-click or tap'n'hold depending on the system).
2. Select New.
3. Input sample length. If you're making a simple chip instrument, 16, 32, 64, and 128 for example are good sizes. Percussion samples need to be longer, like a 100 times.
4. Draw. And don't forget to enable looping in order to get more than just a click out of your wave.
You might have noticed the generator options in the context menu. All the basic wave forms and noises are there so that's good raw material for chipping.