Sere is correct on how to install s-off
here is what he said just simplified a bit:
EVEN THOUGH I AM CONFIDENT IN MY INSTRUCTIONS I DO WANT TO STATE THAT BY FOLLOWING THESE INSTRUCTIONS YOU ARE TAKING ON ALL OF THE RISKS OF ROOTING. I WILL NOT TAKE RESPONSIBILITY IF ANYTHING GOES WRONG. THIS WILL VOID YOUR WARRANTY (ALTHOUGH IT IS POTENTIALLY REVERSIBLE) BUT YOU ALREADY VOIDED WARRANTY BY ROOTING TO BEGIN WITH. SO WHAT I AM SAYING IS, DO THIS AT YOUR OWN RISK.
now that i got that out of the way haha, here we go
1) download the unrevoked forever zip onto your computer
2) plug your phone into the computer (via micro usb) and set the phone as the hard drive as option
3) drag and drop the the "unrevoked forever zip" into the root of your SD card (the root of the sd card is main section of the card. do not put it into any of the sub folders on the card)
4) take the phone out of the hard drive mode by selecting the charging state.
5) unplug the phone and then power off the phone.
6) boot into recovery (by holding volume down and the power button)
7) when the hboot pops up, select recovery and then you should either have the clockwork recovery image or the amon_ra recovery pop up. (i have not used the amon_ra recovery due to i am new to rooting the incredible. i have used clockwork a lot because i had a droid up until recently and i would flash roms, themes, kernel and etc. all the time and i know a lot about it and feel very comfortable using it)
8) when the recovery pops up, go to "install zip" by using the volume rocker or the optical track pad (your choice) and then select it by either pressing the track pad button or the power button (they both do the same thing)
9) go to select zip
10) find the unrevoked zip file and select it
11) there should be a screen that has multiple options to select. all of them says not to install it except for one that will say to install the zip. This is just a safety thing so that people don't accidentally install somthing that they dont want or do on accident. go to install the zip
12) once that is installed then just back out to the main menu and then reboot.
13) now you have s-off installed
good luck man and hope that helps. if this is too simplified i am sorry but i would rather break it down as much as possible for easy to follow instructions so that any new comer to rooting can follow along without getting lost.