Using rtl-sdr libraries from scratch

Hi everyone! I'm so interested about using the rtl-sdr libraries for creating some own applications, but am a bit lost concerning the code structure and the interaction between cmake and the libraries. I have some background in C programming, but I haven't write any code as complicated, and nor of course have I had to use tools like cmake to distribute code, only I've used some Makefiles in order to compile locally a basic code. With this background, I'm trying to manage antenna switches within an array, but I need some new functionalities in the rtl_biast.c code. For this purpose, I have to use the following functions: rtlsdr_set_bias_tee rtlsdr_set_i2c_repeater rtlsdr_i2c_write_reg rtlsdr_close_bt I have modified the code but when I execute cmake and make again, I obtain errors regarding the file dependencies, saying that these functions are undeclared. How should I change the file dependencies/include and recompile it in order to make it works? Could you help me to understand the compilation process in order to arrange my own applications using rtl-sdr libraries locally? I assume I have to study thoroughly the cmake and make advanced topics, but it's a bit overwhelming and I would like to learn about it constructing the code from the basic pieces. Thank you very much in advance.