So when you go to My eBay, aren't you given options to choose from, ie purchase history, selling, watch list, bids & offers etc?  So if you choose the 'selling' option, under here you have a few choices like 'active', 'sold (or orders)', and 'overview'...  Go to overview whilst you have a paid-for item ready to dispatch, and the option 'mark as dispatched' will appear.  Also the option to manually add tracking data appears.