1. Click on 'Share something with your class...'
2. Type in some information about the link, in the 'Share with your class' part. Click on the paperclip icon.
3. Click 'Select files from your computer'.
4. Find the file you want to upload and click Open.
5. This adds the file to a list. You can add more files by clicking 'Add more files'. Once you're ready, click the 'Upload' button.
6. This adds the file to your post. Click 'Post'.
7. The post is displayed like this.
Just in case you were wondering what the Teresa May meme was, here it is in all it's glory!
Note, in a post multiple links and files can be added. For example, see 'Scheduling materials'.