I have 3 NT 520 Pros for different cars of mine. All these notes work for that, which is a little older than your 530. In general, all the support stuff from Foxwell is unreliable due mainly to language incomprehension.

serial number is printed on the back of the unit.
to see password: power on unit (USB or OBDII). on main screen, "setup." "about"

Either from the scanner, or by connecting it via USB and looking at the SN.txt file,
N5B18121********* (I starred my SN + Password out here - it is a single string with the SN and Password, with no space or anything in between) is the only thing in that file.
The screen says:
Product Serial Number: N5B181******
Register Password: 6D****
That serial number is also on the back of the unit.
The password should be recoverable via the login.

I registered myself at foxwelltech.com as username [my email address], choosing my own login password (different vs. the Foxwell unit's password)

Using my username, if I'm at foxwelltech.com, to get to the "Member Center" click on that userid in the upper right of the page.

Register Product - enter SN and Password. (for the unit, not for your login)
Confirms (as of 3/15/2019)
BMW V11.29, released 1/30/2019, and that this is the Latest.
OBDII V6.23, released 1/30/2019, and that this is the Latest.
OS-SOFTWARE V5.50, released 5/6/2018, and that this is the Latest.
UPDATETOOLS V8.71, released 1/24/2019, and that this is the Latest.

Updating the software:
Documentation is terrible. Best to ignore EVERYTHING, including realizing that most of what is written by the application is written by someone who does not understand English.
On a PC, run the FoxScanner V8.73 software. It is possible to launch that from the website.
Connect the foxwell scanner to the PC using a mini-USB cable.
The foxwell will get power from that, and boot up.
Select "Update" from the Application screen (first screen following boot-up) on the scanner, Enter
The FoxScanner application on the PC will now come alive, showing anything that is eligible for updating. For example, it will show the BMW software and the OBD software in black font at the top of a list, with both those items automatically check-marked for updating. All other auto brands will be listed below those, in gray font, not updatable.
Click update. Ignore most of the progress info and instructions since they are wrong.
^^^ That should update the Foxwell. After that, BMW and OBDII will no longer show up on the list in FoxScanner; the only options there will be grayed out, unchecked other brands, AstonMartin, Benz, Chrysler, ...
It looks like the update software is readable on the F: drive, which is the actual SD card in the scanner. The SD card can also be read directly using a microSD adapter.

When connected, and going to disconnect, Windows shows the connected device as: ATMEL AT91 MSD, with USB Drive F: shown grayed out as an apparent sub-device

Updated BMW on 6/27/21.
F:\Scan\OBDII\version.txt said v6.23 (file dated 6/27/2021)
F:\Scan\Bmw\version.txt said v11.30 (file dated 6/27/2021; release date on website shown as Oct 26, 2019)
F:\Scan\Version.txt said v5.50 (file dated 10/19/2018)
F:\SN.txt said N5B18121************ (file dated 1/14/2008)
(SN with password appended)

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2001 X5 3.0i, 203k miles, AT, owned since 2014