Have you followed the instructions/guides for setting up the SPA-3102 with Axon?
I have written one of the guides (check the pinned topics in this forum), and there is also one by NCH. If you have successfully setup the FXO adapter as described in these guides, you should have the ability to
1) Accept incoming calls from a physical exchange connected to the 3102 Adapter
2) Make outgoing calls to a physical line (same as above) connected to the 3102 adapter
In terms of the dialing plans, just make sure the default line is set to the FXO line you setup while configuring your 3102 adapter earlier.
After this is done all calls made from a softphone registered with Axon with that dialing plan should automatically attempt to go through the physical line attached to the 3102 adapter, and all incoming calls should be forwarded on to the appropriate softphone extensions as set in the line's properties.
If you have any further questions or problems, don't hesitate to ask. Please include your SPA-3102 and Axon configuration if possible. (SPA configuration can by opening the config page in a browser and saving the webpage (it will automatically save all tabs), Axon configuration can be saved using the backup-feature in the main window).