Once your abstract has been submitted, reviewed and assigned a presentation type the contribution will be visible to you.
When it is time to upload the slides for your Invited Oral or Contributed Oral please go to 'My Contributions' from the menu selection on the left side of the page and locate your Oral Presentation.
-- Click on the title, which will open a window with your contribution.
-- Locate on the page "Presentation Material" at the bottom of the page, and click on the pencil.
-- Choose Add Materials to the Contribution. You can 'drag & drop' your slides or poster file from the file on your computer.