There is no format tab.
First, select the hard drive on the left (top level, not the indented partitions underneath if there are any yet). Then click on partition on the right. You want to make sure it's set to GUID partition map in options.. and 1 partition (unless you want more). And click partition (or apply or whatever). The parition format should already say MacOS Extended Journaled. And you might as well title the partition "Macintosh HD" if you want to stay true to it.