If you already have a website based on WordPress, you just need to install and enable a plugin. After that, a directory can be added to any website page.
Installation
Go to "Plugins" → "Add new" in the WordPress control panel.
Enter "ecwid" in the search field. The "Ecwid Store" plugin will be displayed. Click "Install."
After plugin installation, click "Activate" and the "Ecwid Store" section will be added to the WordPress main menu.
Authorization
Click "Enable the store" in the "Ecwid Store" section. Use the credentials from the Ecwid service start letter to log into the store.
Adding a store to a website page
Open the page to which you want the store to be added and click "Add store."
A step-by-step guide on how to set up Ecwid in WordPress can be found here.
All manuals can be found on Ecwid support page.