Download main theme, child theme, install both but activate the child theme.
First you must go to your WordPress admin panel.
When you are in your dashboard, go to “Appearance” and choose the “Themes” option
Choose to add a new one
Choose upload theme
Now find FIRST the main theme file on your computer.
First we will choose the MAIN one and install it WITHOUT ACTIVATING IT.
and repeat the uploading process again.
BUT now we will activate the theme.
It is important to activate the child theme and not the main theme.
We check for the last time we have installed and activated the child theme and ready.
In the following video you can see the whole process explained: