Get a permanent host name. You can get one at NO-IP or DynDNS.
Assign your host name to your current IP. If you use some kind of firewall, router or any other way not connected to internet directly, you should configure your router or firewall to make sure that remote users can access your server's port (usually port 8888).
Start SlavaNap
Go to GotNap login page and login using your name and password. Now click on "Server(s)" and add your server.
When you've added a new record for your server you should open settings window in SlavaNap, switch to "GotNap" tab, enter the name and password emailed to you from GotNap for this server, check "enabled" and click "change."
For opennap, you will need to edit your config file and enter the appropriate info, and then start server