ok i would not flash that. that looks likethat could be the official gingerbread update and that can screw your phone up.
1.ok so download this file: Multiupload.com - upload your files to multiple file hosting sites!
2.transfer it to your sd card
3.power off then press and hold power+vol down
4.select recovery
5.select "backup and restore"
6.select "backup" to make a nandroid backup
7.select "wipe cache partitions", "advanced"/"wipe dalvik cache" and "wipe data/factort reset"
8.select "install .zip from sd card"/ find you rom file and select
9.reboot
now the first reboot will take awhile as it has to build dalvik cache. so be patient.
now you are updated!!!!!!!!!!!!!!!!
you can apply that very same steps to flash other roms. you can get most of them on the
http://androidforums.com/evo-4g-all-things-root/284413-roms-kernels-download-page.html.
try mikg2.2 if you want something different or kings alliance 7.6. both are great roms and have senes 2.1 and sense 3.0 which our evo will never get.
edit: also i would highly recommend that you read the
http://androidforums.com/evo-4g-all-things-root/194918-rooting-dummies.html guide. it has a tons of info that you should know.