Styling for address details block of text in Letter head

I’m trying to include the address details and web address on my letterhead (see example below). I have my company logo to the left and want the address details on the right hand side in a vertical line.

But I’m struggling to do this as it appears that you can’t use css in a letterhead and I can’t see how i can use html styling to do what i want.

I’m sure it’s not difficult, hope someone can advise

you can add <style> tag in HTML.