Steps to activate root access:
- Enable the developer option by going to:
Settings > About phone > Tap seven times on Build number;
- Now return to Settings main menu, where you can see Developer options from there;
- Open Developer options;
- Look for Root access setting, and set it Apps and ADB or Apps only or ADB only;
- Now your Device is running Android Marshmallow via CM 13 with full root access.