Download the file to your computer, and move it to the data folder in Wug's toolkit. Should be C:\Wugs_GnexRootToolkit\data
Navigate to the data folder.
Hold shift, right click and select "open command prompt here"
Boot your phone to fast boot (most roms have that option, if not, press and hold vol+ and vol- while booting.
At the command prompt, type the following:
fastboot flash recovery cwmr_touch_beta5_toro.img
After the recovery has been flashed, type the following:
fastboot reboot
ENJOY!!!
PS: cwmr_touch_beta5_toro.img is the name of the recovery file you downloaded, and is current as of posting. If it updates, change the file name to correspond with what ever you downloaded, ie: cwmr_touch_beta5.5_toro.img or cwmr_touch_beta6_toro.img, etc.