Hi Jim,
You can find some information in the Software Developers Guide but I know it's not that detailed, we are working on that. The best way is actually looking in the code examples (included in the BLE stack installer or our wiki) or searching the e2e forum.
If you are interested in the HAL Api for UART you can refer to the HAL Driver API (also included with the BLE stack installer and is found at the default install directory \Documents\hal)
I hope it gives you some starting points.
Best Regards