Since you said your not tech savvy and you didnt actually root the EVO I'm goign to walk you through how to put a new ROM on the phone.
First thing your going to do is download the required files for flashing. I would also suggest looking into flashing a custom kernel to improve battery life. It is just one extra step in the flashing process.
-Download Superwipe to make sure the phone is clean before installing the new ROM
MEGAUPLOAD - The leading online storage and file delivery service
-Download your ROM (I am linking MikG. It is faster, has less bloat, and has the hacked hotspot for free)
MikG info:
Change Log and Info (latest v2.59 - 10/27/2011))
MikG download link:
MEGAUPLOAD - The leading online storage and file delivery service
-Download your kernel (i would suggest lithids more freedom universal)
Info:
[Kernel][Sense][HDMwIn]Evo 4g Freedom-v0.9 Kernel GB MR 2.6.35.10 - xda-developers
Download:
Free File Hosting Made Simple - MediaFire
-Now that you have these downloaded put them on the root (this means not in any subfolders) of your SD card. Connect your phone to a computer and you can select my computer and simply drag and drop onto your phone's drive
-Boot into recovery. This can be done by pulling the battery, inserting it back in, and holding power + volume down to get to your bootloader screen. From there you can select recovery and you will boot into recovery.
-Select Backup and restore and make a backup just in case anything goes wrong. This will save your phone in its current state and you can go back to it at any time as if nothing happened.
-Select Wipe
-Wipe Cache, Dalvik Cache, and Data least least once each. I would suggest doing each 3x to make sure they are clean. Depending on your recovery Dalvik cache may be found under advanced.
-Select flash from zip
-Select the Superwipe and flash it
-Select your ROM and flash it
-Select your Kernel and Flash it
-Reboot
The first reboot will take a while because the phone rebuilds the Dalvik cache that you wiped in the booting process. Just be patient. If you followed all the steps there shouldnt be a problem