Note: These build instructions are only necessary if you want to build the kernel module yourself. If you just want to use a prebuilt module then those are available on the Kernel Modules page.
(backup your old /usr/src if you are using a non-dedicated build box)
git clone https://github.com/pfsense/FreeBSD-src.git /usr/src
cd /usr/src
git pull3. Get the list of branches
git branch -a4. Pick the one that you want to build against
git checkout RELENG_2_4_45. Fetch the patch and build
fetch https://filedrop.c-maxwell.net/patch/upnatom_bxe_patch_v101.patch
patch -p1 < upnatom_bxe_patch_v101.patch
cd sys/modules/bxe
make3. Copy it to your pfsense box
cd /usr/obj/usr/src/amd64.amd64/sys/modules/bxe
scp if_bxe.ko ...
4. Install on Pfsense using the instructions at the bottom of the Kernel Modules page