WD My Cloud 2ex Ultra 2X4GB Hard Drive Query

Hello I have just bought one of these so new to it
1st daft question I am guessing i cannot make the 2 4TB Drives into one big 8TB one?
2) If not I dont want them to replicate between each other I want them seperately with seperate data on them how do I turn this option off so it does not replicate between each other?
Thank You in Advance