If you already have a merchant account with Nextopia:
Go to the Engines page of your SingleFeed account and select Nextopia. Provide a name of your feed file using the name of your domain + .txt. For example, if your store is GreatGoods.com, enter greatgoods.txt as the file name. SingleFeed already knows all the FTP information needed to deliver your feed file to Nextopia. Make sure the “Activate Engine” box is checked, and click the “Save Changes” button.