Well, there's two ways to do this really.

Number 1 is as seen above, feeding compressed air through the carburator (used a lot in Brasil!). You'll need to build a pressure dome around the carb so as to compensate for the increased pressure passing through the carb, or you'll kill the venturi effect a carburator is based on. If you understand your carburator very well you can skip the whole pressure dome and do it the way as pictured above, but you must be very certain that the floatbowl(?) is also pressurized by the turbo so as to compensate for the increased pressure and maintaining the venturi effect.

Number 2 is to place the carb in front of the turbo. In effect, the turbo takes in air (actually, mixture) through the carb. This method is easier to build and tweak, downside is you'll not be able to place an intercooler (instead of air, fuelmixture will pass through and all kinds of weird stuff will start to happen).

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