Welcome to the Community,
... to study for my VCP 5.1 certification ...
first "Lesson" 
, increasing the VMFS datastore on the installation disk is not possible from the GUI (and afaik not officially supported). Since this is a lab environment, you may be interested in increasing the datastore anyway for learning purposes. In this case take a look at e.g. Can't increase Datastore capacity VMFS 5.54
André