tramp is (normally) fully functional when it is initially installed. It is initially configured to use the scp program to connect to the remote host. So in the easiest case, you just type C-x C-f and then enter the file name /user@host:/path/to.file.
On some hosts, there are problems with opening a connection. These are related to the behavior of the remote shell. See See Remote shell setup, for details on this.
If you do not wish to use these commands to connect to the remote host, you should change the default connection and transfer method that tramp uses. There are several different methods that tramp can use to connect to remote hosts and transfer files (see Connection types).
If you don't know which method is right for you, see See Default Method.