To increase the memory, simply shutdown your Virtual Machine.
Go to the control panel of the Virtual Box and go to the properties of your virtual machine. Change the memory size. (must be a multiple of 1024 for smooth working).
Restart the virtual machine.

For training purpose, you do not need to scale up the settings. It is not recommended. You do not need the extra power. But if you wish to then before starting the application services go to the same database initialization file as shown in the videos. Undo the two entries that we did. Save the file. Now start the services. Now navigate to manage concurrent managers screen from System Administrator responsibility and simply enable the concurrent managers manually that we disabled through the SQL statement.