In order to install the IPFire software to the target computer, the target computer’s BIOS may need to be adjusted to allow it to boot from either the CD/DVD or the USB flash drive, depending on which is being used.
(This is not necessary if using a Raspberry Pi.)
Typically, PCs have a built-in network adapter. In order for a minimal firewall to be built, another adapter needs to be added. If you are at all uncomfortable with following the vendor’s instructions on installation, then seek professional assistance with the install. Permanent damage can be done to the computer at this stage if the card is not installed correctly.
As mentioned earlier, a second network adapter can be added to a Raspberry Pi by simply plugging in a USB-Ethernet adapter into one of the USB ports.