Taking a step back here. The better question is more along the lines of "How do I use postgres with kotlin/java"? Only highly opinionated frameworks like spring, django, or rails will come with their own database integrations.
For pretty much any SQL database in Java/Kotlin, the simplest solution is to use the built-in JDBC interface (with a suitable JDBC driver for postgres). However, as Oliver and Ivan pointed out, there are many framework-agnostic database tools out there, like Exposed, jOOQ, and SqlDelight. These tools don't always make things simpler, but they tend to be safer, and can be more maintainable at scale.