The assignments are most likely locked because you need to work through the module content before accessing the assignments. Please click on the course tile on your Canvas Dashboard, the home page will open and from there you can click on the Module tab on the left or on the big green button in the middle of the page labeled "First Module: Welcome!" Then you are required to read the pages and submit the assignments. Once you have officially done that for a module, the next one will open for you.