Http To Https Move

Hi,
I currently have a small web site which is HTTP
I see a notice that Chrome users might see these HTTP sites as NOT SECURE etc.
So i think i need to make the change to HTTPS

This is where i would like to ask for help in doing this.
Currently i am making a backup of the site files & changing all the HTTP text to HTTPS to make a start.
If you can advise please that would be great.
Need to take it once step at a time.

Thanks very much.