Put the following stuff into your monobook.js:
includePage('User:Flominator/flos functions.js');
document.addEventListener("DOMContentLoaded", function() {
insert_link_before("li", "pt-mycontris", '<a
href="http://tools.wikimedia.de/~magnus/mynoinfo.php?user=Flominator">Info-Tag</a>');
show_infobox();
}, false);
done. then, how does it work?