To edit an existing worksheet press  from the list view or  from the detailed view then

To add a brand new worksheet press  

Title your worksheet and provide a description on what it is used for. 

Add a predefined Worksheet Type in order to place your worksheet in a group so that it is easily searchable at a later date. 

Finally before saving decide if you would like for the Worksheet to be able to be created on an ad-hoc basis and if your Worksheet is published for use. 

Once happy press

Now that you have created a worksheet go in to the worksheet builder to design your worksheet.