Put your routers IP address in the preferred DNS server.
OR
You can use Open DNS (which I recommend)
Preferred: 208.67.222.222
Alternate: 208.67.220.220
If you have any decent router, you should be able to assign it a static IP INSIDE YOUR HOME NETWORK. Consult your router documentation of how to do this.
If you are talking about an EXTERAL ip you can't change that as that is a policy of your ISP. Most ISP use dynamic, however you can pay (any i mean pay) and ISP for a static ip. It may be a higher package then the one you have or you may have to switch ISP's.
but: YOU CANNOT JUST ASSIGN YOURSELF AND IP BY SWITCHING DNS SERVERS!!!!!!!!!!!!!! All a dns server does is turn google.com into 64.233.167.147 or computerforum.com into 69.16.225.146 so that your computer can actually access them.
A dns server is like address book. You look up Bob Jones and it tells you that he live 123 Main st. and changing address books does not change where you live, just like changeing DNS servers does not change your IP.