If you have received an email that asks you to upload the Presentation material (a Poster and/or a Video Presentation) before a Conference, but you are not responsible for uploading it, you can add another Contributor as a Co-Author during the Submission process.
Please log in here, go to My submissions and then navigate to the Presentation Material tab.
Click on Submit and then invite the person who is responsible for the upload by clicking on Add co-authors.
Add name and email address and press Continue.
They will receive an email with their own login, and from there they will also have the ability to upload the Content.