When you join a group, you can post content on the Commons by contributing to the discussion board, creating a new doc, or uploading a file. If you want to upload a file, go to Files in the group menu.

You will see a list of files that have been shared by other colleagues. After clicking Upload a New Document, you can upload your file, give your document a display name, and offer a description. Click Save when you’re finished.

Please note that file size is limited to 2 megabytes, so you may want to use a compression tool (such as Small PDF) if your file exceeds the limit.