It’s actually very easy to jailbreal an iDevice. All you need is a jail breaking software such as Black rain, green poison, red snow etc. and te device that you want to jailbreak with a USB connector.
The steps are:-
1) Download the jailbreaking software of you choice and run it.
2) COnnect your iDevice to the computer and turn your device off.
3) After the jailbreaking is complete wait for your device to restart and using Cydia download the things that you want.