Hello,

If you go the Theme Settings > Product Page > SHOW / HIDE ELEMENTS > Show related products http://prntscr.com/klqqsq set “Off”

As for the custom sidebar:

1. Set Full width in the Theme settings > General Layout > set Full width all the pages except Woocommerce pages will be full-width (Woocommerce pages are set in the Theme settings > Shop);

2. Enter the page where you want to set a sidebar and go to SIDEBAR OPTIONS http://prntscr.com/klqy0d You can set location, size and choose the sidebar.

Best Regards