Second Method

 Installing custom ROMs can be very easy or extremely difficult. It's upto you. You should have confidence and don't hesitate.

So let's start. There are many methods to flash a ROM. I would discuss two methods, one with “stock” recovery and the other with custom, though both need fastboot. To use fastboot-

Google — >Platform tools windows. It will be a very small file less than 100Mb and 100Mb is nothing these days. Now extract the zip in a convenient place. Open command prompt there by using shift and right click continuously on the directory and select the familiar option. You will be presented with a command prompt. Here you type fastboot, it will open its help screen. This is useful if you are eager to learn more.

So First method,

Download ROM, keep it in the platform tools directory or sd card. Shutdown your phone. Hold the recovery buttons designated for your phone. For that search google.

Select fastboot there and connect phone to PC. Many people stick around ADB coz they have very less knowledge about that, though not discussing it here.

In fastboot type with the inverted commas, “fastboot flash abcd.zip” (here abcd is your rom name). If it shows signature verification failed then you can try replacing “flash” with “flashall”. Dont know what's flashall? I just told you to explore fastboot. Anyways it will work 70% times.

Second method is discussed by everyone