The child-theme is included in theme package homeradar-child.zip file ( downloaded with All files and documentation option )
Just upload the .zip file to WordPress admin -> Appearance -> Themes screen to install child theme, as HomeRadar parent theme
Then active the HomeRadar Child theme
It’s done.
Then you can add modified code to your child theme files. It will be safe with updates. You can also override HomeRadar theme and HomeRadar Add-Ons .php files from child theme folder. Read the documentations bellow for more details