Editing a Live Site

Hi, I currently have a live wp site https://www.ocscreeding.co.uk which is hosted by 1&1 and the domains are by 123reg. I am looking to update/edit my site and would like to keep the current site live whilst doing this. I have been reading into this and am confused with what is the best method to use. I tried to copy the site with Duplicator Pro but ran into problems and ditched this. I assumed that I could work on the copy from my desktop but was unsure how to access wp with it and how I would upload it to make it the live site. I then read that creating a subdomain might be the best way forward. I have created one with my host (as they offer this for free) but how can I get this to link up to wordpress, do I have to redirect this with my domain register? I have read https://en.support.wordpress.com/map-subdomain/and https://wpsites.net/wordpress-tips/what-is-a-subdomain-how-to-create-sub-domains/. However my host’s c panel looks very different to the ones they talk about. I would really appreciate some advice and real simple steps as I quite new to WordPress. Thanks in advance for your help!