My Banner links without the WWW

Hello everyone! I tried looking around before posting this, but didn’t find anything. I am fairly new to WordPress and PHP, and I am using GoDaddy for my site hosting. The problem is that for some reason Adsense only works if I use www.russbeye.com and not russbeye.com. That is not a problem, as most people type www anyway. The problem is when they user clicks on the banner, it links to russbeye.com, without the www . I am wondering if this problem can be fixed, like a file that needs something to say www . I hope I am clear on this, it’s prety frustrating. Thanks!