User roles

Where is the link to enable viewers to my blog to register with my blog? I don’t see any link or invitation for this function on my blog. I have set the initial user role to be that of “subscriber”, and I have about 64 viewers who have registered at that level. I’m not sure where they went to register. I am notified when someone does register, but I don’t know how they do that. I’m using Suffusion theme 3.7.3. Please tell me where the link for this feature is located on my blog. Thanks.