One of the key purposes is to give the new believer an opportunity to publicly tell the story of how God lifted them out of their sin-debt and hopefully inspire others to come to God, through faith in the finished work of Christ on the cross.
The question was “How do you USE a baptism?”
My answer was about the “purpose“ of baptism and was based on my personal experience- “How do I use...”. I have no scriptural support for the stated purpose - only the effect I have seen baptisms have on unsaved (and saved) people who witnessed the testimony of the new believer.
The REASON we baptize is because we are commanded by Scripture to do so.