Replace fuel injector problem

I am trying to replace fuel injector number one. Everything I have read here says to relieve fuel pressure first. But nothing says how! I have looked elsewhere and other places either did not mention it at all or did not mention how either. So, how do you relieve fuel pressure?

There is a knob on the backside on top of a metal tube. What is that and what does it do? Does it relieve fuel pressure? Does it cut on and off fuel to injectors? I do not think so, because I have turned it all the way on and off and it does not seem to change anything that I can tell. But I do need to know if it needs to be close or opened (whether it does anything or not)?

My other problem is (which is far greater), I replaced the fuel injector number one and put it all back together. When putting the fuel rail back in, I made sure they all lined up, but when I tried to push down, one side or the other would put up and get unaligned. So, I lined the all up and tightened the bolts down and they seem to go down into the intake, but I worried if they were seated or not.

So I finished putting it all together and hooked the battery back up and turned the key over and waited twenty seconds and then cranked the car. It cranked fairly normal, but still sounded rough. I started backing out of garage to take a test drive. But I noticed while rolling downhill in the short driveway, that I was leaving a trail of gas.

It was spewing gas from underneath the car, right where the engine meets the transmission. I am fairly certain it is coming from the fuel injectors and traveling down the backside of the engine at the firewall. But naturally I cannot see it from the top with everything back together. Even shining a light through the upper intake manifold I could see one of the injectors (I think one) and I did not see any liquid, but who knows.

Pulled it back in the garage and took the Upper Intake manifold back off. Number five looks wet. The other do not. But I have a fan blowing across the front of the car and it could have dried the others and just not five, who knows.

Does anyone have a suggestion? Could one fuel Injector spew a massive amount of fuel out? Or could it be all of them or some of them and I cannot tell? Or is it somewhere else, like the knob I pointed to? Or could the upper intake manifold not have been sealed properly? I do not think that has anything to do with fuel, I just want to cover all my bases. Could it pinch or displace the fuel rod somehow?