SharePoint 3.0

I need to find a way to solve a problem with SharePoint.

Let me explain what I have:
In the main page of SharePoint I have a tab called Business Development which takes me to a webpage. In this webpage I have two links to webpages, one is Marketing and the other is Proposals. Marketing and Proposals has more links with more websites.

Now I need to get rid of the Business Development tab and create two tabs called Marketing and Proposals.

I don't know how to do this. I've spent a couple of hours trying to find a solution but it would be helpful if someone has any suggestions.

I downloaded SharePoint designer.

If I need to be more clearer let me know.