To install-it, use the insmod tool. Only super users can load and unload kernel modules.
$ sudo insmod /hellokernel.ko
To see if the kernel was load successfully use the lsmod tool, this tool will list all kernel modules loaded in your system.
$ lsmod
Now, if you look into the kernel log you should see the glorious message "Hello Kernel!".
You can do this with the dmesg tool.
$ dmesg
To unload the kernel module, use the rmmod tool.
$ sudo rmmod hellokernel