mas-bandwidth-netcode provides a static library and header:

    find_path(NETCODE_INCLUDE_DIR netcode.h)
    find_library(NETCODE_LIBRARY netcode)
    target_include_directories(main PRIVATE ${NETCODE_INCLUDE_DIR})
    target_link_libraries(main PRIVATE ${NETCODE_LIBRARY})

mas-bandwidth-netcode uses libsodium for encryption and authentication; link it as well:

    find_package(unofficial-sodium CONFIG REQUIRED)
    target_link_libraries(main PRIVATE unofficial-sodium::sodium)

On Windows, also link ws2_32 and iphlpapi.