Pulling the lever towards you will apply the choke, then pushing it away from you disengages it.
most people will apply full choke and start the bike, then slowly take it off as the bike is able to stay running on its own and leave it idle until warm up. This is wrong , and you should refrain from letting it idle till warm.
Turn the ignition to on, LEAVE THE CHOKE OFF, press the starter and SLOWLY pull the choke towards you until she starts up. Once she up and running, leave it for about a minute or so (put your gloves on and get comfortable), and ride off with the choke still on . Keep the revs low, and dont run it hard until its warmed up. Keep riding until you can gradually turn the choke off , that may be a couple miles. This is the proper way to start your bike and make sure you have a long engine life.
When you apply full choke at startup, you risk flooding the engine. the ninja needs very little choke to get it running.