It's not a stupid question at all.
There is a part of the GRO website where you can search the indexes to find that information and order the certificate directly from them. It is here:
https://www.gro.gov.uk/gro/content/certificates/indexessearch.asp
You start off by choosing birth or death.
Working through an example of looking for a death. Once you click on death it will then ask you what year it was registered and you can also include a range eg +/- 2 years.
You can then enter the surname and sex of the person you are looking for. It helps to enter more information, like their first name, as well to help narrow down the results.
It also has an option to include similar names just in case you're not sure of the exact spelling.
You then hit search and it will come back with all the entries that match.
For example, I was once looking for the death certificate of a woman by the name of Muriel Hubbard who died in 2019.
So I put those details into the search and it came back with three different Muriel Hubbard's that died that year. It gives the quarter they died in, the place they died and also their year of birth along with the reference information that is needed.
I happened to know where in the country the Muriel I was looking for died and I also knew her date of birth so I could identify which one of the three Muriels it was that I was looking for.
From there you click on whichever is the right person and it comes up with the options for ordering, which are Certificate, PDF and Digital Image (although for newer records you only get the choice of Certificate.
When you then click on Certificate (or one of the other choices) it then takes you to a page where you can order the certificate for £12.50 and all the information is pre-filled.
It's a similar process for looking for a birth certificate, except, you will also have the option to include the mother's maiden surname as well.