When adding one css property to something, use ( to open it, and ) to close it.  Put your property inside, starting with the name of it (e.g. height) surrounded by single quotes, followed by a comma, and then what you'd like to add (e.g. 200px) also surrounded by single quotes.

$('div').css('height', '200px');

When adding multiple css changes to something, use ({ to open it, and }) to close it.  Put your properties inside one after another followed by a comma.

$('div').css({
  'width: '200px',
  'height': '200px',
  'border-radius': '10px'
});