E-commerce is a recently developed platform on Freshdesk which would enable you to bring the Ebay channel into the helpdesk. This is a feature enabled upon request and so kindly contact us on support@freshdesk.com in order to bring this as an option on the admin tab. 

Once this is enabled, you could see this in Admin -> Channels -> E-commerce where you can add a new account. This new account would need your eBay site information and you would be able to assign product, group and such.