We've been through this before.
Simply being a CWI in no way infers you are qualified to develop a WPS. There are CWI's with the background and experience that have the knowledge to develop a WPS, but if you have to ask how, what, and why, you clearly are not ready to undertake those tasks.
I want to cry when a CWI calls me and asks where to find the tensile test results to list on the prequalified WPS.
AWS offers a course on how to qualify a WPS and how to write a prequalified WPS, but that is beyond the scope of knowledge required of a CWI. The CWI is expected to recognize a WPS, he is expected to know what the information means and where to find it on the WPS, but he is not expected to know how to write the WPS.
AWS B5.1 Table 1 lists what job responsibilities the CWI is expected to be able to perform. Every CWI is expected to read it and QC1 before taking the CWI examination. It would appear few do read it.
A CWI with a few years of experience under his belt and if he has the opportunity to work with a Welding Engineer or if he has attended some of the more advanced courses offered by AWS or ASME can learn how to write a WPS, but it isn't part of the CWI examination and it isn't covered in any depth by the CWI seminars.
I can't tell you how many times I've seen entries on the WPS like: "Progression - right to left or left to right." It brings a little sniffle to my nose every time.
Best regards - Al