There is 2 ways to flash(remember im a newbie but this has worked great for me) i have read A LOT...
1)Download ROM MANAGER there are ROMs there u can flash..
What i do is download the ROM u want to flash connect phone to cpu with usb in DISK DRIVE mode. drag the ROM to ur sd card.open ROM MANAGER, go to INSTALL ROM FROM SD CARD, scroll down select the ROM u downloaded, wait a few mintues and enjoy...
2) flash through RECOVERY.... (restart phone hold power and vol down)
{What i do is download the ROM u want to flash connect phone to cpu with usb in DISK DRIVE mode. drag the ROM to ur sd card. restart phone vol down go, select RECOVERY then to go to sd card pick the name of the ROM then press power to start. wait a few minutes n enjoy..}
How to flash depends on the ROM itself. both ways will work.. through ROM MANAGER u might have some apps that dont open properly.
Hope this work for you it has worked for me after fooling around with it. just would like to pass around info i found. its really not that hard. this process takes about 10 min either way....