There are three ways you can rename a worksheet, and the only difference between them is the way in which you start the renaming process. You can do any of the following:
Double-click on one of the existing worksheet names.
Right-click on an existing worksheet name, then choose Rename from the resulting Context menu.
Select the worksheet you want to rename (click on the worksheet tab) and then select the Sheet option from the Format menu. This displays a submenu from which you should select the Rename option.
The sheet will be in single quotes because it contains a space, and the mandatory period (.) always falls outside any quotes.