You need to use the kldload utility loads file.ko into the kernel using the kernel linker. /boot/kernel directory containing loadable modules. Modules must have an extension of .ko. The kldload utility exits 0 on success, and >0 if an error occurs.
Example: Load module called foo
Type the command as follows:
# kldload foo
# kldload -v foo
To list loaded module use kldstat as follows:
Some modules such as pf, ipfw, ipf, and others may be automatically loaded at boot time when the corresponding rc.conf statement is used. Modules may also be auto-loaded through their addition to loader.conf file.
kldload command options
From the man page:
-n Don't try to load module if already loaded. -v Be more verbose. -q Silence any extraneous warnings.