Hi Joseph,
basically you using Outsystem bootstrap action which is make default Create entity action only.
if you need to update data then you have to do things on same action-
1. use createOrUpdate action instead of createaction
2. Add filter on a aggregate based on a unique column
3. Assign Source Identifier


In this case Data identified by aggregate than data update else Create new.
Hope this will help you.
Regards
Rahul