You have two options to interact with MetaWear:
1. Using the Android/iOS API.
You just need to know how to program in Java and Objective-C, pull up Xcode, Eclipse, or your favorite IDE and start toggling LEDs directly from your Smartphone. You can download example code and API documentation from Github.
2. Write your own firmware.
You simply purchase a Nordic debugger, write some C (up to 256KB of code) in the Keil/Eclipse/IAR IDE, and flash the Nordic BLE SOC through the exposed debug/programming port. You can find documentation and support on the Nordic website.