how do I enable the root user from the Directory Utility?

How do I enable the root account ? I don't see any options related the system user. Do I enter the server as "localhost"? What do I select here? System Software Overview: System Version: OS X 10.10.2 (14C1510) Kernel Version: Darwin 14.1.0 Boot Volume: Mac OSx Boot Mode: Normal Computer Name: A MacBook Pro User Name: thufir (thufir) Secure Virtual Memory: Enabled Time since boot: 1:03 Hardware Overview: Model Name: MacBook Pro Model Identifier: MacBookPro9,1 Processor Name: Intel Core i7 Processor Speed: 2.3 GHz Number of Processors: 1 Total Number of Cores: 4 L2 Cache (per Core): 256 KB L3 Cache: 6 MB Memory: 4 GB Boot ROM Version: MBP91.00D3.B08 SMC Version (system): 2.1f175 Serial Number (system): C02HH5JQDV33 Hardware UUID: FBB1FF0A-6EAC-5423-9E8F-405B181EF5F3 Sudden Motion Sensor: State: Enabled