Assistance needed please for responsive site Options

[IPBR21054]

Evening,
I have learning difficulties but once guided I can normally take it from there.
It’s the starting I have issues with.

This is my first post so here goes.
This is the site in question https://www.theremotedoctor.co.uk/exmoor.html

I’m happy with the look etc on my Pc but stuck when it comes to being responsive for mobiles & iPads etc.

Please can you assist with the code needed for my css file.
I can then look & what it does & experiment with it.


Many Thanks.