Echoing what's already been said, look around this (and other) kart sites before you even draw a picture. Decide what you want your kart to do - is it for playing in the dirt, or will it run asphalt as well? Will it turn left to go fast, or are twisties in it's future? Off road and trail? Single wheel drive or live axle? Scrub brakes, band brake, or disc? There are lots of options.
Once you decide what you want your kart to do, see if you can websearch and find one already built and copy it the best you can.
Most people are very helpful, if you can actually contact whoever made the kart you're using as an example you may get the specs you need the easy way. If not, don't forget that "Back in the day", many a winning race car started life as a paper drawing and was constructed using chalk lines on a garage floor.
Once you get your basic measurements just pay attention to detail and you'll be find.
If you get stuck, just ask - chances are whatever problem you have someone here has already found the answer to!