Hey Alangreg,
I’ll go over the issues in the same order:
1). Please excuse me, forgot one more thing: try selecting the necessary sidebar areas (in your case – Sidebar) in the “Replaceable Sidebars” section in the top left corner of the Appearance Custom Sidebars admin section and clicking on “Save changes” underneath.
2). The unzipped php file should be uploaded into the following folder inside the WordPress directory of your website: /wp-content/themes/Ikebana – via an FTP client or using your hosting provider’s file manager, available on most hosting management admins such as cPanel or Plesk.
Sincerely,
Andrii / Satori Studio