To replace a catalytic converter is a tough job dude. So if. You have never done a DIY task befpre than i would recommend you not to perform this task. But if you have done a lot of DIY tasks, then following steps will help you in replacement:
First you need to raise the vehicle completely by putting jacks on all the four tires. Replacing catalytic converter is typically under the car job, so make sure you raise your car safely to actually go inside the car.
Now, you need to locate the catalytic converter which you can notice in thr exhaust system which is rectangular or circular shape.
After finding the converter, you need to remove the oxygen sensor before the converter. You will need wrenches and similar tools to remove it. So make sure you have all the tools required.
Keep the oxygen sensor aside and unscrew the converter which may be tighten rustly. So be careful with it.
So now you have removed the catalytic converter. To replace it woth a new one consult your dealer or car manual fpr proper dimensions and specifications of the new convertr that you will need install.
Not installing the new converter is same process as of removing it. Place the new converter to tje same position where the old one was. Now tighten the nuts using the tools. Install the oxygen sensor again.
Now you are good to go. But one more thing to remember, do not preform this task with engine on and hot exhaust system. And please do not avoid the jacks that you are using to raise your car. If you do that, you are inviting a tragedy home. So make sure that you carefully and safely raise the vehicle.