First thing, verify that you are currently running Froyo build EB13 on your Epic. Verify that the ROM that you want to use is an EB13 build and is EXT4 capable.
Download the ROM that you want. Keep it in the .zip format and place it on your SD card.
Download the
Default Stock Dual FS kernel For EB13 and keep in the .zip format and place it on your SD card.
Download
THIS and leave it on your windows computer.
Reference this thread if wanted....
Per the directions on XDA (with some added commentary):
1. Unzip the file from directly above to your desktop.
2. Go into your phone and Go to settings->Applications->Development and turn on USB Debugging.
3. Now double click run.bat in the folder you unzipped. (If you are on linux ./run.sh from the folder)
4. Wait for everything to happen.
5. Use the THREE BUTTON METHOD to get to CWM3.
6. Wait for the conversion operation to finish.
7. DO NOT REBOOT!!!!
8. IF YOU ARE ON AN ODEXED ROM (DEFAULT OTA) THEN YOU NEED TO REFLASH A ROM AFTER THE CONVERSION!!!!!!! ODEXED ROMS DO NOT GET RESTORED PROPERLY!
9. Flash the Default Stock Dual FS kernel For EB13:
http://efragtv.com/android/EB13-DUALFS-KERNEL.zip ***You should already have this saved to your SD Card if you followed the directions above***
10. Enjoy CWM 3.0.0.5/6
In completely untested and unconfirmed theory, step 7 says that you cannot reboot. I believe this to mean that your phone will not properly load until the steps are completed.
I would STRONGLY advise making a nandroid backup first (prior to doing any of this). Additionally, it is important that you boot into recovery using the 3 Button method (instead of ROM Manager or Quick Boot). Additionally, don't forget to wipe Data, Cache and Dalvik Cache (found under advanced) three times each prior to flashing a ROM.
Volume Keys scroll up and down in Recovery. Camera Key is your enter button.