1) Hit Ctrl + I at the Manufacturer Logo or when you see the Following Screen:

2) In order to Delete Existing Raid Configuration, then select 2nd Option and Hit Enter:

3) Then select the Raid Partition you want to Delete and Hit the Delete Button:

4) Hit "Y" to Confirm:

5) To Create a New Raid Configuration, select the 1st Option and Hit Enter:

6) Enter the Name, Type and Size of Partition you want to Create, then select Create Volume and hit Enter:

7) This is how the New Created Raid will look like: