How do I add a subheading to my site?

[RJSChi]

The site is: https://www.strichardschichester.co.uk/
And I'd like to put a smaller subheading under the main 'Catholic Parish of Our Lady and the Saints of Sussex' title, saying 'Chichester - Bosham - Selsey - Witterings'. Probably in grey. 
There's no subheading option, that I can see, so I guess it means an edit to the HTML, but I don't know how to do it. Can anyone help, pleases?

[whitemonkey]

@RJSChi 

i think the only way is to use a page with a header   that inclues a pre loaded sub header   included in the relevant theme

[RJSChi]

Thank you. I can't find an appropriate theme that has a subheading but I think I've found an alternative solution.