White screen – can't login

Hello, Can anyone help please? I’m new to WordPress and I think I just wrecked my website!
I was trying to customize my Customizr theme by adding a text box on to the home page.
To do this I thought that all I had to do was paste a code into the Editor page. When I pasted in the code and clicked ‘Update’ the screen went blank. Now I can’t access my website at all. I can’t even login to the wp-admin page as that is blank too. In short, I can’t do a thing!

All suggestions gratefully received please??? Thanks.