1. The first step is to open the Classwork  tab for the Google Classroom.

Then click the assignment.

2. Click View assignment

3. Click Add or create

4. For an already created Doc or file click Google Drive

5. To create a file that is automatically linked to the Google Classroom use Create New

6. Find the file.  Recent is often the easiest way to do this.

7. Click the file

8. Click Add

9. Click Turn in

10. Check the summary of files to make sure everything needed is attached.

11. Click Turn in.

That's it. You're done.

Interactive tutorial