You forgot to include the padding in pixels. Here's how you can do it,
$('#loginform1').css('padding-top', '120px');
The complete code should look like this,
$('#login').on('click', function(){
$('#loginform1').css('padding-top', '120px');
});
Although it's not necessary to specify the pixels as mentioned by another commenter, I recommend doing so to avoid any confusion with plain CSS. If there is a problem, it could be related to your ready handler. Try wrapping your code inside the document's ready event,
$(function(){
$('#login').on('click', function(){
$('#loginform1').css('padding-top', '120px');
});
})