You can jump to a symbol by using the -f <symbol> option on the Source Insight command line when you start Source Insight.
sourceinsight4 -f myfunc
This will position to the symbol named "myfunc".
You can also simply give the name of the symbol on the command line without a special command option, as though it were a file name. In this case, Source Insight will try to determine whether the symbol you specified is either a file, or a parsed symbol. You can list as many symbols on the command line as you like, just as with file names.
sourceinsight4 myfunc fcb init
This will open all files where the symbols "myfunc", "fcb", and "init" are located. See: Command Line Syntax.