In order to install amsn, or even to be able to launch it, you will need to compile it first.
To do so, you must first configure the package by executing the command
> ./configure
You must have the tcl-dev and tk-dev packages installed on your system, please refer to your system package management software or website in order to find these packages and to install them prior to running the ./configure script.
Once the configure script finished without any error, you can proceed with the compilation, it is as simple as typing :
> make
You can now launch amsn by typing 
> ./amsn
Or you can install it with the command
> make install
Then you can use the 
> amsn
command to launch future sessions of amsn.
You can also create a .deb and .rpm package by launching respectively the command
> make deb
and
> make rpm

For any other help, please refer to the FAQ at http://amsn-project.net/faq.php or the wiki at http://amsn-project.net/wiki or the website at http://amsn-project.net or visit the forums of amsn at http://amsn-project.net/forums, but make sure you search for an answer to your question before asking it, it might have already been answered.

have fun.
