Not sure exactly what you are asking but if its how to make new actions and add them to an NLA here are some screenshots:
First switch to the DopeSheet window
Then Switch the Dope Sheet to Action Editor.
At that point you should either see a Add New Action Button or a text field where you can click the plus button to add more actions. Add an action animate the cube, make a few different actions. When you have all the actions you need, switch to the NLA editor.
At this point if you double click on the snowflake icon?? You can then add action to the NLA editor and everything now work similar to how Blender 2.4x use to do things. No idea why this step has to be done to get the add action function to work, but it appears to be the only way (at the moment).
Lots of big pics but there was no easy way in text to describe the steps. Seriously messy way at the moment but, maybe it will get improved.
Also attached is the Blend file if it’s any use
ActionNLA.blend (65.4 KB)