On the top navigation of SharePoint, you have the links automatically created to link to the other pages, but there could be times where you want to add more links or change the top link navigation. This guide will help you do this.
Login to your SharePoint site as an Administrator or a user with Full Control and on the top of your SharePoint page, click Edit Links
Once the edit functions come on, you can click the X to remove a link, or click on the work link to add a new link.
Once you click the Link button, a window will pop up. You can now enter a Name of the new link, and the URL of where you want to go when you click it. This is a great way to navigate between different Site Collections or External Websites. Click OK when finished.