My wd showing only 1.81tb in 4tb

I recently decided to purchase the 4TB model. I just hooked everything up and everything seems to be working correctly except the drive under “My Computer” only shows 1.81TB available I tried to change RAID1 to RAID0 but RAID0 is not highlighting can someone pls suggest step by step instructions.

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Try making sure the connection are secure remove the drives then place them in again