Which drive should I encrypt?

[irob]

Hello,
I just bought:
WintoUSB
Bitlock Anywhere.

I was able to successfully use WintoUSB ad install Windows 10 Pro on a Sandisk Extreme Pro USB Thumb Drive.
I would like to install Bitlock and Encrypt the Windows on the USB.
When I start Bitlock Anywhere it shows the hard disk (C: My computer) and 2 removable drives D: (this contains Boot, EFI, Bootmgr) and E: (WintoUSB which contains a file Win2USB.VHDX).

Which one should I select?

Thanks
iR

In this case, you should encrypt the boot partition on the Win2USB.VHDX file. Please insert this USB drive into a computer that is running Windows, attach the VHD(X) file on the USB drive in Disk Management, then use Bitlocker drive encryption to encrypt the boot partition on the mounted VHD(X) disk. Here are the detailed steps:
1. Open Disk Management, right click 'Disk Management', then click 'Attach VHD'.


2. Select the VHDX file on the USB drive, then click 'OK'.



3. The virtual disk is mounted as I:



4. Use Hasleo BitLocker Anywhere to encrypt the I:.



Reference:

What are system partitions and boot partitions:
http://www.easyuefi.com/wintousb/faq/en_...tions.html


I GET THAT THE FILE/DRIVE IS ALREADY ENCRYPTED??????
What would the password be then?
I want to add that it is from an image (ISO) of my Windows on computer.