Hi @lori_graham Welcome to the Canvas Community! While there are various ways one can work around this, a timed assignment is not actually possible other than by making it an online quiz and setting it to be timed, as outlined in the various options shown here: https://community.canvaslms.com/docs/DOC-10152-415241475 . Depending on what you had in mind for this assignment, you could in theory make it a one-question quiz where they have to upload a file, as outlined here: https://community.canvaslms.com/docs/DOC-12878-4152125612 . That is exactly what instructors at my own institution have done when they have asked similar questions to yours, Lori. Hopefully this is an option for you.
(Those links, by the way, lead to the current version of quizzes. If you are on Quizzes.Next, there is information on setting a time here, and information on file upload questions here. You can tell if you are a Quizzes.Next next institution by the way that you create a quiz. The traditional engine has quizzes added via the Quizzes menu item; Quizzes.Next adds them via the Assignments menu item.)