First step: you need to have a seller account on ebay
Consult directly with ebay the conditions to import the product feed in XML format.
01) Access the Control Panel
02) After login click on Store Feeds
03) On the ebay line click New File
04) Fill in the form and select the products, after clicking Confirm
05) Click XML to download the file.
If you want to add a crontab for daily or weekly update you can use the parameters as shown in the ebay line
To import go to: https://www.mip.ebay.com/settings/channelmanagement