replacing a 10 inch Pella 39-395 RH Hinge arm Assembly

Hi, Scott.

Before I give you my explanation, I recommend watching the video below to get a better idea of what I mean.

I've never personally installed these hinges but it looks like they work the same as the one in this video. For starters, you will need to remove the sash from the main frame of the window. After that, you will need to remove the pivot arm screw which mounts the long pivot arm to the window sill. Next, you will need to remove the sash by sliding the nylon guides on the hinge arm out of the main frame of the window. With the window sash removed, unscrew the old hinge off the sash and screw on the new hinges. 

Make sure to take note which hinge is at the top and which is attached to the bottom. It might be helpful to take some photos of how the hinges are attached before removing them so you get it installed correctly. You will also need help with doing this job. Someone will need to hold the sash while you are trying to remove it from the mainframe.