I can see where the confusion below comes from and I agree that you need to structure your question a little better.
If you are seeking a dynamic IP address for your computer, it is likely as stated below that you already have one. This is the most common configuration. Static IP addresses on the other hand are useful if you plan to run web services such as email or web servers on your computer.
The other possibility here, is that you are seeking advice on obtaining a dynamic domain name service. This would be the type of service that allows you to make a domain name point to something like your home computer. There are many services like this available. Just search the web for Dynamic DNS. Two options that stick out in my mind are DYNDNS.ORG and NO-IP.COM. Both of these services offer what I have outlined above.
Hope this helps. If not, restate the question.