You can create new tabs in Safari, assuming you have Tabs turned on in your Safari preferences, in two ways. The first is to press Command+T. But you can also create a new tab by clicking in the blank space to the right of the right-most tab label at the top of the Safari window.
Related: Drag Tabs to Windows in Safari, Disappearing Tabs in Safari, Tabbed Browsing in Safari, Open Tabs From Top Sites, Cycle Through Safari Tabs.
