First you to to make sure you have added some variations that could be applied to products.
To create variations select ‘Variation‘ from ‘Web Commerce’.
You can select the type from ‘None‘ or ‘Disposable‘ variation type.
To add the variation simply insert the Name and Standard and click on Add button.
Click on edit button of the product that you would like to add variation to.
Click on the Variation option from the left panel.
You can then choose from standard or enterprise variation
Then from the variation types choose the created variation that you would like to apply.
Then click on generate.
Then from variation combination tab click on the ticks to activate the variation.
You can add attributes such as price, amount and image. When you are done click on update.