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Ummm, it's not an A-Z of how to do it and module building is really a skill that requires some background understanding in html and php web-coding.
You also need to know how the XOOPS core system works, including the use of smarty, because many modules integtrate core functions as part on the connectivity of the rest of the site.
If you are just at the beginning, you might expect a considerable learning curve. If you are analytical, then examining how other modules work, is a good start.