You set the networking adapter into bridged mode (virtual box settings). That's all.
If you want to be able to access your development server from the production server, you need to port-forward port 22 to your development computer/virtal box IP.
To access the file system on the production server, you can use scp to copy files back and forth. I wouldn't recommend it however, it's a pain in the ass.
I would recommend you sshfs.
The way sshfs works is, it mounts the remote file system in your local filesystem.
Then you just open, edit, save, copy/paste files there, and sshfs does the scp data-transmitting stuff in the background.
sshfs theUserYouWantToLoginAs@ip.of.target.computer:/ /path/to/folder/where/you/want/to/mount/the/remote/filesystem
sshfs email@example.com:/ /mnt/sshfs
PS: I would use ssh keys, not a password. Passwords are too weak.
To generate a key:
ssh-keygen -t rsa -b 4096
This generates id_rsa and id_rsa.pub
id_rsa.pub you echo into the authorized_keys file in the .ssh folder in the home directory of the ssh user on the target machine
copy id_rsa.pub file to the target computer
cat ./id_rsa.pub >> /root/.ssh/authorized_keys