How to create a new SNP Matrix?

Hi all- I'm trying to create a SNP matrix and have been following this documentation that corresponds to the snpSTATS Package : https://www.bioconductor.org/packages/release/bioc/vignettes/snpStats/inst/doc/data-input-vignette.pdf

However the document only shows how to access sample SNP matrices. How would I create my own matrix? (Referring to pages 2-3 of this document)