Proper Window Sill Pan Installation

My new 132″ X 18″ window came with a two-piece sill pan that, according to the mfg instructions must be installed. I’ve installed plenty of windows before but have never needed a sill pan .
What is the proper installation method for this?
Should I caulk it to the bottom of the window itself or to the fram/flashing ? I will need to shim the bottom a little to center this in the opening
Thanks,
Paul
Replies
Is this a PVC sill pan designed to be glued together in the middle?
The main thing I would do is get some slope to it. I use cedar bevel siding under window pans, whether they're made of sheet metal or membrane material. And, do not caulk behind the bottom flange.
Thanks for the tips. It's two piece aluminum, that typical of my mfg'er, is not actually quite long enough. I have additional material on hand though.