E-commerce features are available in case your administrator configured accordingly your Opigno platform (see more at Enabling e-commerce features).
A new field will be available in training's edition page, allowing to define a price for that training:
In case no price is entered in that field, the training will be considered as free and users won't have to go through the checkout process to register to that training.
By default, the price is for an unlimited access to the training (no recurring payment implemented by default).