behind the engine I saw steam and then coolant spilling.

What is the question? Could be a leaking heater core, heater hose, core plug, etc. If that steam showed up right away, before the engine warmed up, coolant leaking onto hot exhaust system parts is a good possibility. If you find it leaking from a short rubber hose hanging down on the passenger side of the firewall, under the hood, suspect a leaking heater core.

As soon as I started the truck the steam was coming like from the upper center area on the back of the engine then I saw coolant dripping fast. Is that going to be difficult to repair.

There is no way I can tell what is wrong. A heater hose takes a few minutes to replace. A heater core can take all day. If a core plug is leaking at the rear of the engine, the transmission may need to be removed to get to it. The first step is to determine where the coolant is leaking from. Post a photo of it if possible.

Okay, I will post the picture in the morning. Thank you for the quick response.

This is where everything is happening. Is this just a hose I can screw on or I have to buy the whole piece?

That looks more like an emissions pipe that's part of the exhaust system. Your best bet is to visit the dealer's parts department. They will help you identify the part on a drawing on their computer system. If they can't tell you what is commonly replaced, they will run into the shop and grab a mechanic who is familiar with it.