Add it to Podfile:
pod "pjsip-ios", git: "https://github.com/Anakros/pjsip-ios.git"Include needed headers in a Xcode project:
#import <pjnath.h>
#import <pjlib.h>
#import <pjlib-util.h>You can build it manually from sources, just run pjsip build-script.