Hello,
If you are asking whether you can upload the PPT so that it appears when you eventually start your session, that is not possible. If you are asking whether you can ATTACH the PPT to the meeting invitation that attendees receive so they can print/download the slide deck in advance of the session, that IS possible.
Nothing that is to be presented/shared DURING the session can be uploaded in advance while scheduling. We tend to go into our sessions 15-20 minutes in advance of start time to upload all documents.
Hope this was helpful in some way.
Eric