Hello
please download and install a plugin named as woocommerce, activate it after installation.
you will then need to add a new page named as shop and set that page as the shop page from the woocommerce settings area.
you will be able to add products using the woocommerce plugin and those products will appear in the shop page.
you may also use full documentation of the woocommerce plugin, click here to check https://docs.woocommerce.com/documentation/plugins/woocommerce/getting-started/
Thank you