1) Welcome to the Party!
2) As you are obviously new here, I have some suggestions to help us all help you:
When you post, please post your entire configuration including (but not limited to) your installation method and vicidial version with build.
This IS a requirement for posting along with reading the stickies (at the top of each forum) and the manager's manual (available on EFLO.net, both free and paid versions)
You should also post: Asterisk version, telephony hardware (model number is helpful here), cluster information if you have one, and whether any other software is installed in the box. If your installation method is "from scratch" you must post your operating system and should also post the .iso version from which you installed your original operating system. If your installation is "Hosted" list the site name of the host.
If this is a "Cloud" or "Virtual" server, please note the technology involved along with the version of that techology (ie: VMware Server Version 2.0.2). If it is not, merely stating the Motherboard model # and CPU would be helpful.
Similar to This:
Vicibox X.X from .iso | Vicidial X.X.X-XXX Build XXXXXX-XXXX | Asterisk X.X.X | Single Server | No Digium/Sangoma Hardware | No Extra Software After Installation | Intel DG35EC | Core2Quad Q6600
3) Goautodial is the name of the installation disk you used. The actual software is Vicidial (it can also be installed from an .iso image downloaded at Vicibox.com ... same software!).
4) You have not described your network configuration at all. If your server has a public IP, external access is pretty easy: just modify the firewall in the OS to open the ports for the IP addresses of the users who need access. If it has a private IP, your router will need to be configured to allow access. For instance, you can open TCP port 80 to the IP addresses of your users on the outside of the router and forward that port to the internal IP of your Vicidial server. Then they have Web access. Similar process can be used for SIP access (except UDP port 5060 and port range 10000-25000 should be either forwarded or set up as a "trigger" port).
5) There have been many other requests on this topic for both this system and hundreds of other Linux applications (running CentOS and all the other Linux OSs across the world). This is not so much a Vicidial question as it is a simple linux networking question, except that SIP phone calls can complicate the process by requiring that 10000-25000 port trigger or forward mentioned above.
Happy Hunting