Maybe a dead cdi or mag coil, grab an ohm meter and check your leads. Think it's like 60 or 360 ohms lol on that magneto. They fail like nothing. Also that thing jaguar always mentions, there are screws that hold the mag in place, it sometimes has too much shellac or coating on the mag making a good ground connection bad. You might need to scrape it off.
Also check the kill switch, if it's in kill mode (depending on the kill switch type) it won't let it run.
Check the wires again, black to black and blue to blue and leave the white covered in tape or cut it off.
Just throwing this one out there make sure there's gas in the tank since that's important. Also turn the petcock (tank valve) to the on position since these bikes usually only work if it's on.
Make sure your wire connections aren't shorting on the frame, if the blue wires have bare metal touching the bike frame then you have a short and it won't run, put tape on it.
The clutch is easy, put the cable on the cable arm. Make sure it's tightish, usually parallel with the wheels is a good position. Then squeeze the clutch lever in and lock it. Turn the flower nut (with your hand pressing on the round silver plate it holds in) and turn till it gets snug against the plate, now turn it the other way just a tiny bit so you can roll the bike without turning the motor. If it rolls freely then you turned it enough, if you let the clutch lever go free then you should be able to turn the wheel and the motor will turn without slipping. Readjust cable slack, put covers on and try to make it go.
Check your spark plug gap? If it's too small it might not work, it might not work if it's too big too. I installed or found installed plugs with closed gaps (probably dropped it or whatever) and they don't work good at all...
Make sure the carb is snug against the intake, air leaks are real motherf***ers.
Make sure the headbolts are torqued right, again those airleaks.
First time starting is always going to be a bit harder. Find a big hill and hop on, hope for the best.