You can use your same testing results for St. Thomas that you are using for the BVI as long as they both are within the 5 day window of arrival. Assuming that if you are arriving on Wednesday that you will test on Friday or Saturday (I would do Saturday because I like to have a buffer day in case there are any flight delays.). Once you get your results, go onto the travel portal: https://www.usvitravelportal.com/ and fill out the application. Make sure to take a screenshot of your tracking ID. You should immediately get an email verifying your submission. If you don't get an email it might have gone to junk mail or you put in your email address wrong. This is where knowing that tracking ID number comes in handy. Go to:
https://www.usvitravelportal.com/tracking-application and put in your information. It will then give you the status of your application which since it is so early on in the process will most likely be pending. It takes anywhere from 15 minutes to 3 days to get your approval back but it is a pretty easy system.

Maybe more information than you were looking for but figured it is better to be informed and learn from other's mistakes than have to figure it out yourselves.