Hi.
here we go.
download this
DeodexedMeritRoot.zip . It is the same as what you have now, but it is rooted and deodexed(cleaned up some unneeded files).
Rename it to "update.zip"
make sure its on your sdcard, then turn your phone off. Hold the volume up button, the menu button and then press the power button while holding those down.
This will boot you into recovery mode. ( you can move around with vol up and down and pik with the home button. Select "wipe user data" and it will install this rooted version. when it is done installing reboot, it will take a couple minutes, but will load and you will be rooted.
so to summarize, download that, rename it, put on sdcard. Boot into recovery, wipe data and let install.
Easy as it can get no pc needed.
EDIT-BAckup any contacts, sms etc you need. You will lose data.