Home Assistant remote access static Ip Domain add SSL certification

Hi, I try to add SSL to my home assistant.

When I go from an external network my.domain.com HA is shown to me and I can log in.

Now I want to add SLL for a home assistant.

I got two files

numbers.crt
numbers.key

and don’t know how to add certificate how to configure them witch my domain.com

any help. Please Please write to me to step by step I’m far far from an expert