In Case you want to upload a white background image as the main image, then follow the below steps:
Step 1: Click on Products in Left Hand Menu
Step 2: Click on export/import
Step 3: Click on Product Edit / Upload
Step 4: Select the Profile
Step 5: Export the File
Step 6: Open the File
Step 7: Under Column Name Image - 1, provide the image URL of the image which has the white background
Step 8: Save the File
Step 9: Navigate Back to the Same Section
Step 10: Browse the File
Step 11: Click on Import
This way your product will be upload to Catch with a white background image as the main image.
Note : In case the product is variant then you need to update the same image in the Variant Image Column as well.