You have not provided us much info to answer your question.
What is the Model of the array?
what is the flare on the array.
If its a CX4 is Vitual provisioning installed on the same.
Please get back to us with the above info so that we can assist you further.
Leaving the 1st 5 drives that is vault drives you can use any number of drives from the array to create a storage pool. If FAST VP is enabled then even the different types of drives can be done in a pool.
The method would be different if you're using Navisphere or Unisphere, but generally, you go to the place where the Storage Pools are located and find the Create select and then decide what type of storage pool you want to create (raid group or Pool) and select the raid type and then the disks.
It would help when you ask a question to provide the array model and what interface you're using - Navisphere or Unisphere, what version of flare on the array.
Also, click the Help button and do a search for creating storage pool - Help is very good for these types of questions.
Unisphere- is a software which is being used from flare 30 onwards. For using Unisphere one array in your domain should be at flare 30. Then unsiphere can also be used to manage the other arrays running below 30.
The white papers for the same can be downloaded from :
From Flare 30 onwards its free but will depend on your contract if you are upgrading.
For creating pools on the arrays, as Glen said...refer navisphere help. Its the best place for such guidance.