I really can't tell you all you need to know on a web site, but one thing you need is a slave pin. That is a short pin, slightly smaller in diameter than the rear trigger guard pin but only long enough to go through the trigger guard. With that, you assemble the sear and sear spring, then put the guard in place and insert the regular pin, pushing out the slave pin.
As to your question, you install the hammer first, then squeeze the lifter and hand together against the spring so they can be inserted in front of the hammer. (You might find it easier to put the hammer in, but not install the hammer screw until you get the trigger in.) Then put in the trigger pin, the trigger spring, and the trigger guard, with the sear and spring installed as described. Then install the hammer spring, put on the grips and you are done.
HTH
Jim