You will need to install OS X on the drive first. Since this will erase the drive first, wait until you have done it before transferring files from the other drive. Alternatively, you can clone the 1 TB startup drive to the new drive once the new drive has been partitioned and formatted.
Clone Yosemite, Mavericks, Lion/Mountain Lion using Restore Option of Disk Utility
Boot to the Recovery HD:
Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.
1. Select Disk Utility from the main menu then press the Continue
button.
2. Select the destination volume from the left side list.
3. Click on the Restore tab in the DU main window.
4. Select the destination volume from the left side list and drag it
to the Destination entry field.
5. Select the source volume from the left side list and drag it to
the Source entry field.
6. Double-check you got it right, then click on the Restore button.
Destination means the 6TB drive. Source means the 1TB startup drive.
Once the clone has been completed use the Startup Disk utility from the Recovery HD's Apple menu and set the Macintosh HD volume on the 6TB drive to be the default startup volume. Restart.