With respect, you probably should suspend your effort to work with guacamole until you get your basic remote desktop functionality working.
The purpose of remote desktop is to allow a user sitting in front of machine C (for client) to get a desktop on machine S (for server), and use that machine. S can be in a datacenter, or anywhere. If machine C is a Windows machine, its user can use the program called "Remote Desktop Connection" to connect to machine S. Start that program, then give it the hostname of your machine S, and it will display a window showing a desktop of machine S. You can then do things on machine S as if you were sitting in front of its monitor, keyboard, and mouse. For this to work, machine S has to be running a remote desktop server application that listens for requests from other machines (machine C). Windows has one of those built in. Linux does not. Linux offers two (or maybe more) kinds of remote desktop setups: xrdp and xvnc. xrdp is compatible with Windows's Remote Desktop Connection. xvnc uses a VNC client on your machine C. You'll have to install that client. On a Linux server, you have to install one (or both) of those servers and start it on machine S before you can connect to it from machine C. Use your favorite search engine to look up xrdp or xvnc, and figure out how to install or start it. It's not hard. Then figure out how to connect from your machine C to machine S without Guacamole, using another remote desktop client package. Then, and only then, start working with Guacamole again. Guacamole serves to replace the Remote Desktop Connection program on your machine C, and other users' machines, with a web application. That makes it easier for casual users to gain remote access to your machine S -- they just visit the Guacamole web application you set up. Good luck.
