First go to: https://www.pfsense.org/download/
and select the following:
Version - Choose your prefered version or i must recommend the latest version.
Architechture - select 64-bit if you want 64 bit and 32-bit if you want 32 bit.
Mirror - USB Memstick if you are using flash drives and ISO if you want to use it like burning it on a cd and etc...
Console - for me i choose VGA
Then click on download!!!
Any comments question is highly appreciated just comment down below and i will give you my best time answering your queries.
Next: Creating a Bootable PFSense in a flash drive
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it's me,
@jriel