Hello,
If you want to do some changes in php files just copy required php files in the child theme directory and edit them. More information about child theme you can read here: http://codex.wordpress.org/Child_Themes.
The style changes should be done in the custom.css of parent theme. Here is a video tutorial how to create custom.css: https://www.youtube.com/watch?v=Qok2zRedRMY&feature=youtu.be. The tutorial is recorded for Legenda but actions are analogical for IDStore.
Regards,
Jack Richardson















