Before you proceed, you need Spaces installed on your phone.
How to delete a post/notice?
Step 1 - Open the Space > Navigate to the Post/Notice that you want to delete (You can delete the post only if you are the Owner/Admin of the Space or you are the one who created the post)
Step 2 - Click on the three-bullet icon at the right corner of the post.
Step 3 - Select Delete from the drop-down list and confirm.
You are done!