How do I hack someone computer or mobile by his/her ip address?

 How do I hack someone computer or mobile by his/her ip address? 

First of all you need to know the difference between the two types of ip address,i.e.

 static ip and dynamic ip.

 Most of the people doesn't have a static ip. Only some big organization or companies have static ip address. On the other hand almost every common person have dynamic ip connection. Dynamic ip means that, every time you disconnect and reconnect to the internet, your system is assigned a completely new ip address.

 Whereas in static ip, it doesn't matter how many times you reconnect to the internet, your ip would be the same everytime

If you are planning to attack someone who is having a static ip connection then you can move on. But if the victim is having a dynamic ip connection then you can not guess the validity of that ip.

 In this case if the victim disconnects and reconnect to the internet then you have to obtain the ip address once again. So i think you got the differences between the two types of ip address by now.

Now back to the question. Even if you have the victim's ip address, its not going to help you unless there is a backdoor in the victim's system. By backdoor, i mean an open port that can listen to and reply back to your data packets. This can even be done if there is a vulnerable application present in victim's system. The best example of a backdoor is something known as the trojan horse or RAT standing for remote administration tool. So i think you've got answer to your question.