Go to:

Listings > Import

1) Click on the "Import from Platform" and select the desired platform you would like to import your listings from the drop down list.

2) The desired listing will take awhile to be imported. You may check back in a few minutes. Don't forget to reload the page if it doesn't appear.

3) Repeat steps 1 and 2 for the rest of your platforms.

4) All your listings from all platforms are now in OneCart! :)