CAT exam is on 26th November 2017. There is not much time left. You have 3 months left in case you are aiming CAT 2017.

Also you are doing your bachelors privately that means you have enough time assumingly.

Also to prepare in these 3 months:

3 months is sufficient provided you utilize the time left with you appropriately. Around 3 hours per day on weekdays and Around 4 - 5 hours on weekends/offs.

Importantly be regular with your study plan and be sincere because if you divert you will lose your vision.

Attempt and analyse your mocks/tests. Pay heed to the topics and types of questions that you are consistently doing well at. Find these questions in your real CAT and tackle them. Also, your analysis should reveal to you which areas are difficult for you - in terms of time spent as well as in terms of accuracy. Focus on improving these areas. If this takes much time, avoid them at all costs in the actual CAT. also you will get familiar with the online mode.

In case you are asking for CAT 2018, then you can start the preparation from and when you are comfortable. A year preparation is good if you are ready for next year.

All the best!