Thanks for your interest in Narayana and STM in particular. I am not sure if you saw it yet but we do have a guide on how to use STM and it does have a section on Containers: Narayana Project Documentation in particular you will note the volatility configuration option.
I noticed that the STM javadocs don't seem to be on narayna.io so I created an issue to record this: https://issues.jboss.org/browse/JBTM-2652
We have a quickstart that shows something similar to what you were asking for: https://github.com/jbosstm/quickstart/tree/master/STM/jta/src/main/java
Hope that helps,
You can use the @TransactionFree annotation on the methods to tell the container not to create a transaction when the method is invoked. As Tom mentioned, check out the docs and let us know if there are things that need clarifying.