Installing Child Theme

Hi
I am new to wordpress and coding and just anything web development,I have not yet published my website,I am still working on it so it looks good now I installed responsive theme versin 1.9.6.5 and would like to add its child theme but don’t know how,I am yet to upload wordpress on my host but installed it using cPanel softaculous program,how do I upload my wordpress website on my host the add child theme to tweak it to my specification? I am new to just everything so please be gentle and considerate.