If you want to setup left header menu first Go to admin panel > Appearance > Customize > Header and Footer > Header.
And to setup left header menu select header type as a “left menu”.
You can also assign individual left header menu from page, post, products.
To assign left menu on Page, navigate to admin panel > edit page on which you want to left header menu. And for more understanding, see below image.
Note: You can assign left header menu for the single post and product from the Hongo post settings. The same process applies for product settings.
Tip: Left menu header set in full row layout for proper view please see below screen shot.
