First of all just download Nexus Root Toolkit 1.8.5 from here, here or here. You can downlod previous version Nexus Root Toolkit 1.8.4 from here.

Unlocking, rooting, relocking and unrooting simplified! (and much more!)

VERSION 1.8.5 - This program will automatically bring together all the files you need to unlock and root your device in a few clicks, or flash it back to stock and re-lock it. You can also use this program to backup/restore all your important data, flash zips, set file permissions, push and pull files, install apps, generate logcats/bugreports, and much more! With the included file association options, you can perform tasks like flashing zips, installing apps, restoring android backup files, and flashing/booting img files with just a double click! The program includes a full featured interface for automating tasks in TWRP, enhanced restore features, an in-built auto-updater/notification system, ‘any build’ mode, advanced restore features,’NRT- Live Log’ for viewing the adb/fastboot cmds that are run in the background, quick tools utilities, and tools for taking screenshots/screen-recordings. All the latest Android builds and Nexus devices are officially supported including the new Nexus 5, with full KitKat support for all the newly upgraded devices. The program intelligently and selectively downloads the files it needs for your device and makes sure you are using the latest files available. The program can even auto-detect your device and build. The main changes in this release are full 4.4.4 support, improvements to the updater, and general code enhancements and optimizations.

Supported Nexus devices:
· Galaxy Nexus: GSM Models (both yakju and non-yakju builds)
· Galaxy Nexus: CDMA/LTE Verizon Models
· Galaxy Nexus: CDMA/LTE Sprint Models
· Nexus S: Worldwide, i9020t and i9023 Models
· Nexus S: 850MHz, i9020a Models
· Nexus S: Korea, m200 Models
· Nexus S 4G: d720 Models
· Nexus 7: Asus Tablet
· Nexus 7 3G: Asus Tablet
· Nexus 7 v2 (2013): Asus Tablet
· Nexus 7 v2 (2013) LTE: Asus Tablet
· Nexus 10: Samsung Tablet
· Nexus 4: LG Phone
· Nexus 5: LG Phone

Instructions:

1. Select the correct device and build (what you are currently running)

2. Configure your drivers if you haven’t already using the driver guide (If you aren’t sure use Step 3 of the driver guide to test your drivers).

3. If you need to, backup your important data.

4. Unlock your device

5. Root your device

6. Enjoy! ^_^

Learn more about each option by mousing over the control, dynamic tooltips will provide you more information, also each button displays a message about what it does first.
So the best way to get familiar with the toolkit is simply to press the buttons and read what it says.

What’s new in Nexus Root Toolkit 1.8.5 (July 30th, 2014)
· Removed legacy/redundant driver methods and replaced them with fully automated driver solutions via DpInst.exe. The toolkit no longer uses third-party driver installers and extensive pictorial walk-through’s. Now there are three fully automated driver solutions (Google, PdaNet, & Universal) which only require one click to install. The Raw/manual method and pictorial walk-through is still included.
· Enhanced the NRT Uninstaller to provide an option for also uninstalling the drivers.
· All auto-downloaders now present a “retry download” option if it fails in addition to the manual download method.
· Improvements to the updater, progress bar won’t get stuck on 1% and say mismatch, it will now always go to 100%, and if you get the mismatch you can retry the download.
· Just like the root procedure, advanced utilities > flash perm > “flash recovery” button now also renames recovery-from-boot.p to ensure recovery sticks.
· Android L-preview added, full support will be included when its officially released.
· Full KTU84Q 4.4.4 support.
· Updated toolkit to use the latest platform-tools and Google driver files from the SDK.
· Bug fixes and optimizations.

via www.wugfresh.com