Using client account to point to server

Hey there I am new to the forums I recently installed the own cloud client on the qnap server I am wonderinf to and if or how to correctly point the desktop client to the own cloud server client, and can people out side the local network point to this server as well to backout there computer say have a client use my personal server for their backups

There is only the owncloud server. Before you get more into this QNAP installation, be aware of some serious limitations: