offsite backup target

I am looking to use my 5N as a backup target located offsite (my home).

I have a couple of ways in mind one is to install an FTP server on the drobo and send my files from work.

The other way might be to install a VPN client on the drobo to make it connect to work and then send files that way.

I can not get any FTP server to install.

I’m open to suggestions, but I am a total noob in linux.