How to add Letterbox to the Video I have shot?
There are various ways to add letterboxing in PP.

Some ways I have done are:


creating a Photoshop file (or finding one already made) and using an adjustment layer to apply it. ( I used this post http://whoismatt.com/cinemascopetutorial/)
when exporting you can use the crop function to chop the top and bottom off
using an adjustment layer again but cropping it in 132 from top and 132 from bottom ( believe)
make a new Sequence, using Custom settings that's 1920 x 816.
google has loads of sites if you do a quick search letterboxing in adobe premier


I hope some of the above help in a way