As far as I know the DJetro doesn't have Launch control - Only the PowerFc Pro does.
However, incase I'm wrong here's how -
Go into the Settings menu - rev/idle - the 1st F/C E/C setting is your L/C rev limit(should be the 1st one underneath your normal rev limit).
To test, on a warmed up engine set it to 3000rpm and with the staionary rev to 4000rpm. If you've got L/C it'll stop at 3000rpm with an almighty set of bangs and pops! If it goes past 3000rpm you don't have it.
I had mine for about a year and it's great fun