Uh.... just don't do it wrong? 
Nobody can advise without more info (what you are using to try and upload and what specifically is going wrong)
If using the eBay app on a mobile device, or iPad, etc you need to ask in those sub-forums:
https://community.ebay.com/t5/Mobile-App-Android/bd-p/androidapp
https://community.ebay.com/t5/Mobile-App-iOS/bd-p/iosapp
On a desktop, try another browser, Firefox 31 is working fine for me as of this moment. Edge, IE, and Chrome tend to have a lot of problems with eBay.
If you are seeing a specific error, describe it.
