You can add files to schedule tasks from the task pop up on your published or draft schedule.
Click to open the task pop up and you will see the option to "Add a file" in the lower right.
Use this option to attach a file to this schedule task, add a description or label, and choose whether the file should be shared with trade partners.
Click "Save" on the task pop up after uploading the file, and be sure to publish your changes.
In the Gantt or Task Views, you can use the "Notes/Files" column to easily see which tasks have attachments at a glance.
You can also add files to your schedule templates, and all added documents will carry over when you copy the schedule template to a new project.