TDLib should be prebuilt and installed to local subdirectory td/:
cd <path to TDLib sources>
mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX:PATH=../example/swift/td ..
cmake --build . --target install
Then you can open and build the example with the latest Xcode.
Description of all available classes and methods can be found at td_json_client and td_api documentation.