Constantin,
You can find the no-OS software on the GitHub: no-OS/ad9361/sw at master · analogdevicesinc/no-OS · GitHub
Essentially, you have to call just the ad9361_init() to initialize the part. The function takes as parameter a structure (default_init_param: no-OS/main.c at master · analogdevicesinc/no-OS · GitHub) that contains all the important initialization settings: duplex type (FDD, TDD), LO and sampling frequencies, gain control mode (manual, automatic), ... etc. Some of these settings can be also modified after the part was initialized using the corresponding functions (no-OS/ad9361_api.h at master · analogdevicesinc/no-OS · GitHub).
Take also a look on the wiki for additional information: http://wiki.analog.com/resources/eval/user-guides/ad-fmcomms2-ebz
Regards,
Dragos