In Sharpei you have 2 options to add a Selling Plan to your product variants.
1. Add a Selling Plan inside a Variant:
With this option, you have to go to the product variant in which you'd like to assign a Selling Plan by editing it.
Steps:
Go to 'Inventory', 'Variants'
Select the product variant you want
Click on 'Edit'
Click on 'Add Selling Plan'
Save
To see the video explanation, go to the following article: Edit and add a Selling Plan to a variant
2. Assign your products to a Selling Plan:
With this option, you can add your products in bulk directly into a Selling Plan from the configuration panel.
Steps:
Go to 'Configuración', 'Selling Plans'
Select the Selling Plan to which you want to add your products
Click on 'Assign Products'
Select the product variants and click on 'Assign'
To see the video explanation, go to the following article: Configure your Selling Plans to the Assign products to a Selling Plan in bulk part.