I don't know the specific device, but things that start out as Windows
boxes usually tend to have secure boot enabled these days. It's a while
since I last fought Windows but I think you may have to boot into
Windows and then tell it you want to do a maintenance boot and then
catch it during boot to get into the BIOS to turn off secure booting.
It's a rigmarole, and if you get the timing wrong you have to start again.
From my notes on a variety of machines over time the most common key to
press during boot to get into the BIOS is F2, with DEL being the second
most likely alternative.
I read the bit on the web site about replacing the SSD as meaning if you
wish to increase storage size, not that you can't write to the existing
one (but I could be wrong).
Final note: you might want to look at OPNsense as an alternative to
pfSense. I'm in the process of switching as pfSense appears to be more
commercially oriented these days.
--
All network cabling aspires to the condition of macramé.