You will need a local bitcoind on your Armory computer.
Your local bitcoind is able to connect with a bitcoind blockchain on an other server/NAS in your local network or external server.

Be aware of the security risks!!!
Armory expect your local machine, bitcoind, Armory and connections to be safe, with this settings you undermine this basic principle.

Only advisable if you KNOW what you are doing.

On your local bitcoin.conf:
connect=[IP of bitcoind server]
addnode=127.0.0.1
rpcconnect=[IP of bitcoind server]
whitelist=255.255.255.0

Also set in Armory settings the rpcuser and rpcpassword of the bitcoind server.