All you need is 

If already done that download Android SDK. 

Once everything is done proceed to next step

Getting Phone ready

Open clockworkmod recovery and create backup of your apps on External Sd card.Then download any Rom .It will be in rar file so first open it and extract "Boot" file only and keep it on your computer and now put the rar file in Internal Memory of your phone.Now Switch off the phone and connect the usb with computer (not with phone just with pc) and then hold volume up button and connect phone to usb. You will see a blue led glowing.

Installing Rom

When the phones in fastboot mode ( blue led glowing) Copy the Boot file you extracted to Platform tools of Android SDK. Now go to platform tools ,Keep pressing shift and right click on any place in the folder.Then click open command prompt here. There type fastboot flash boot boot.img and press enter.

When it completes type Fastboot reboot  . Wait for some time and blue led will turn Pink for few seconds Just at that time keep pressing Volume up button . Now you are in Recovery mod  [select using lock key.]

First go to wipe data/factory reset. Then go to advanced and wipe davlik cache.

Then go to flash zip from sd card and select the rar file. Now after installation is finished your phone will take some time to start during first time but then it will be normal.