Customizing password protected pages

I recently moved to using the Hello Elementor theme and mostly it’s been great.

However, I have a few pages protected with WordPress’s standard Password Protection – and the text, password field and submit button that appear before a password is entered are horribly laid out, with no section/element margins, bad alignment and so on. (Although the submit button has inherited its styling correctly from the Elementor Site Settings.)

Does anyone know how I can use Elementor to correct this? Or failing that, another approach? I’ve seen a couple of examples of custom CSS being used, but only for other themes and it’s hard to apply to this one.

Many thanks for any guidance!