We are attaching a few screenshots to help you understand how to post a link on a Group's wall.
1. First Create a new WriteUp.
2. Then go to the Group where you would like to post the link to your WriteUp.
3. When you click in the "Post Something" area the Add Link option gets enabled.
4. Now click on the "Add Link".
5. Next copy paste the path to the new WriteUp as shown below:
6. Now if you click on the "Links" tab, you can view the links that are attached to a particular group.
Hope this was helpful. If you have any further queries, please feel free to ask us.