The item you have pictured will need a few strokes of a saw and file before you inlet it. First, the forward extension is likely too long and will need shortening so it doesn't interfere with the lug on the trigger guard. And secondly, you need to file draft on the sides of the plate so that you can inlet it with out gaps. I am not quite sure what you mean by "the hole for the trigger"? The hole to accommodate the trigger's blade is inlet with drilling first, then narrow chisel for removing the webs of the drilled holes, and often a thin flat chisel for widening the cut. It needs to be long enough and deep enough so that the trigger will interact with the lock's sear arm and clear all the wood to move freely. If you had a blueprint drawing of the profile of the rifle with those parts drawn in, you would be able to see how much to cut off and where. Guessing at it would never work for me. And what someone else has done on their rifle won't help you much either.
I'll try to post some pictures of a rifle I built hopefully showing the spots you want...IMGBB still won't upload my images, darn.
OK, I'll try for one picture showing a drawing of the relationship. Nope, won't upload. I'm befuddled.