RaptorTechnique has some good info on engine tuning & starting procedures. If you just want to start it up and idle it, you can probably just disconnect the throttle linkage and adjust the throttle by hand, then you don't have to figure out how the TX has the throttle set up. Just have a firm hold on the blade grip and be ready to pinch/pull the fuel line to the carb if revs too high (cutting the throttle off completely should kill it as well). If you're not sure if the engines been tuned properly, you can follow the raptortechnique instructions or your engine manual to get a rich initial setting for the carb. Start with just a little throttle at a time, you want enough to start and idle but not enough to get the RPM high enough to engage the clutch.

If you want to do more than just start it and idle it, you should probably figure out how the throttle is setup on your TX so you can rev it up remotely while it's strapped down. Main thing is to make sure you don't have your throttle stick too high, or an idle-up setting turned on when you try to start it!