My b2evolution Version: 2.x

I've edited the welcome page, but when I click on click on a link to go to the Comments section, the URL in the address bar includes "welcome-to-b2evolution", and I would like to change this to something appropriate to the website. I've been trying everything I can think of and searching for the answer, and can't find anything. I found the phrase "welcome-to-b2evolution" in the URL "filename" box on the Post editing page in BackOffice, but changing only caused the link to stop working, as it looking for URL "filename" welcome-to-b2evolution, I guess. Could anyone tell me how to fix this?

Also in my attempts to fix it, I created a new category, and can't delete the old one, I just get an error that says "1 posts within category through extra cat". The "extra" box is not checked for any post in any category (I only have 1 post and 2 categories, one of which I 'm trying to delete), so if anyone understands what might be going on there, it would be most appreciated, also :) Thank you!!!