In case you want to manage product description through the App then you need to first make the following changes in the Settings under Product Management
Step 1 : Click on Settings
Step 2 : Click on Product Management
Step 3 : Scroll Down to Auto Sync
Step 4 : Disable the Checkbox for Description
Step 5 : Click on Save
In order to change description of product one by one follow the below steps :
Step 1 : Click on Products in the Left Hand Menu
Step 2 : Click on All Products
Step 3 : Click on the Edit Product Icon next to the Product
Step 4 : In General under Description make the necessary changes in the product description
Step 5 : Click on Save
Step 6 : Click on Product in the Left Hand Menu
Step 7 : Click on All Products
Step 8 : Select the Product
Step 9 : Choose Bulk Action - Publish Listing
Step 10 : Click on Action
The description will be updated on the Catch once the Feed is completed on Catch without error.
In order to change description of product in bulk follow the below steps :
Step 1 : Click on Product in the Left Hand Menu
Step 2 : Click on Import / Export
Step 3 : Export the Products in Excel
Step 4 : Edit the Description in Description column of the Excel Sheet
Step 5 : Save the File
Step 6 : Import the File under the Import / Export
The description will be updated on the Catch once the feed in completed on Catch without Error
You can also refer to the following demo video - How to Change Title and Description without changing on Shopify?