You will also get the option to format the drive while installing Windows. Disconnect any other drives you have in the system before erasing the drive to ensure you select the proper one. Obviously this will erase all data on the drive.
If you select "Custom" install then on page that shows drives select advanced then DELETE all partiotions. This will clear both the OS partition and the tiny 100 mb system partition. then just select the NOW unpartitioned drive to install to.
PS This also wipes ALL data from the SSD and as tomatthe stated,, disconnect all other HDDs when installing OS on SSD