If you are living with a cat that has not been trained, it is possible that they will avoid their cat scratching post and use your new sofa instead; they will choose their own spot to urinate rather than go to the litter box.
It is also possible to train your cat to use the proper equipment for their activities.
However, if you approach the training in a way that they don't understand then your efforts will get little good results.
The first and most basic principle is that your cat does not respond to punishment.
If your pet refuses to use the cat scratching post that you provided and you punish them, they won't understand what they are getting yelled at for.
They don't believe that they have done anything wrong.
You see, an activity such as scratching is very natural.
This provides a way for your cat to exercise, stretch, and work their claws.
Yelling at them for this simply does not make sense to them.
They don't understand that you are trying to punish them because of their choice of location for that activity, not for the activity itself.
Same principle applies for using the litter box.
Relieving themselves is a natural response.
They don't immediately understand why you would be upset with them for doing something natural.
The remedy to this is use positive reinforcement.
When you catch your cat using the cat scratching post to stretch and claw, give them a little treat and speak to them in a positive tone telling them how good they are.
Make a point to try to catch them doing good things and reward that behavior.
If you find your cat going back to an inappropriate place then you may give a little hiss to deter him, but do not yell or punish.
Instead, encourage them to go back to the cat scratching post or the litter box which you provided and repeat the positive reward response that they will crave.