Hi,
here you can find the instructions:
.war file is nothing more than a zip file, that is extracted by tomcat on startup in the webapps folder of the tomcat root.
If you want to add the print plugin to the extracted folder, add the files in the instructions in the webapps/mapstore folder
If you want a deployable war that already contains the print plugin, add the files to the war (zip) file, in the same folder indicated in the documentation.