Is your Evo flashed to boost already or are you looking to do that?
Do you know if it is rooted yet?
Here is a link to rooting the phone:
You can post back here what it says in the bootloader screen and we can tell from that, the status of root or not.
Pull the battery, wait about 20 seconds, put the battery back in.
While holding the volume down button, press and hold power.
A white screen will come up with info on it.
Just post back here what it all says.