What every you do.. don't follow the advice of some here and put it on a selector valve. The last thing you want to do if rough seas.. or anytime for that matter.. is to have to shut one engine off, then select the fuel valve to the other port and fire up the other outboard. There are also times when trolling/downrigging with the kicker that you'll need the big motor fired up to make a turn into/against the wind, having a selector valve negates that ability.
I also NEVER shut one engine off before starting the other one. I can guarantee that if you do that you'll find you have dead batteries at the worst time and be dead in the water.
As long as the kicker has a good squeeze bulb and the check valve is working in it, just tee the line to the main engine and enjoy the ability to fire up either motor at will without playing with fuel valves.
The only thing you may want to add in this day of ethanol fuels is a water seperator. Buy one with one inlet and two outlets and hook to each motor.