when i am not logged into my forum I noticed that signature links are not clickable, but when I am logged in they are clickable...

How can I change it so that they are always clickable regardless if user is logged in or not ?

It's obviously something that you interpret incorrectly or something which provides an unknown issue for me.

miniBB signatures by default are saved as static content. If allowed, they already are saved with built-in URLs. By default, these URLs are displayed to everybody, it doesn't depend on the login status.

Also, miniBB doesn't use the "parsing-on-the-fly" and so it's impossible to display URLs for guests of members, if there is no special add-on or code installed.