how can I prepare random process in communication system for gate ece

There are good resource available on internet for

Random process

For video lecture I would suggest you to go through lecture of Mondal sir from IIT Kharagpur and their is a book named Random Variable and Stochastic process by Papoulis it is Bible for Random variable and random process with detailed explanation

Also you can look lecture of Prof. Surendra Prasad of IIT DELHI, Prof. Aditya k Jagannath from IIT Kanpur

Feel free to ask me in the comment box if you are having any further doubts

hope you find it helpful

Good Luck!