Before sewing your covers and signatures into a bound journal, you need to make holes for the thread to go through that line up consistently. I used a Western Multiple Signature binding with four-holes described p. 147 ff in Making Handmade Books by Alise Golden. The Coptic Stitch binding would work just as well and Google will return plenty of documentation links for that. Determine the number of holes you need, fold your template paper in half so the crease runs along the 6 inch dimension, and mark out your holes. Put a "T" at the top edge of your template and pre-punch the holes with your binding awl or upholstery needle.
Put little marks to indicate the top edge of your covers and five signatures.
Open your catalog or small phone directory in the middle. Open the cover or signature and place it so the middle crease lines up with the "valley" of the catalog. Place your template over the crease and be sure the top of it lines up with the top of your signature or cover.
Punch through the pre-punch holes with the awl or needle.