Your action should already be set up. When that's ready to go (like you would normally) File> Automate> Batch [choose your action and source]
Here's where the fun begins: In the same Batch window instead of clicking 'Okay' right away adjust the File Naming which is part of the Destination (Folder> Choose)
File Naming has a helpful 'Example' which will change as you adjust the drop down options. I usually type in for 'Document Name' the name of the project and my name then + (change default extension to 2 Digit Serial Number)+ (in the third drop down>) extension. It should end up looking like this in your Example: ProjectName01 (.ext)
Alrighty, hope that was helpful, cheers you guys!