Excuse my ignorance, but please forgive me for asking a stupid question!

The FAQ tab will answer a lot of your questions. Members here have shared their knowledge of the various iterations of units over the years to develop guides explaining the steps needed.

The Garmin won't play the different sound files without first installing a particular version of the sound driver file (SOX). Icons and custom point-of-interest (POI) files are loaded using a Garmin provided loader program that will allow you to set distances to trigger an alert sound or audio message. Once you have looked through the FAQs and experimented a little, the members here will be able to provide additional help for specific problems and issues you are having.

It sounds as though you already know how to load Custom POIs to your DriveSmart 65 using Garmin's POI Loader program. That's a good start. Adding custom sounds and custom icons to your custom POIs is the next step.

Two quick thoughts to keep you on track:

-as Box Car states, if you're using a PC to run POI Loader, you will need to add sox.exe to your computer—see FAQs for sox version and location. Mac computers do not need sox.exe.

-your Drivesmart 65 can only play wav audio files, not mp3 files, so when downloading custom audio alerts, always choose the wav file.

Audio: http://www.poi-factory.com/node/25730

Icons: http://www.poi-factory.com/node/4359

(Note that this icon FAQ provides information about creating custom icons. You don't need to know how to create an icon if you just download the already-made icons available here at the POI-Factory.)

I know nothing about Alexa so someone else may have to offer help with that.

After reading the FAQs and trying to add icons and audio, come back if you have questions.

Here are a couple of videos I done that may help. https://youtu.be/iuHHgAnOeMo and https://youtu.be/RxlkiVQU41Q

Make sure all your files for the POI are labeled identically....
Dissimilar named files will not work