Hi,  You can't share reports under "My Reports".  "My Reports" is a little bit like "My Documents" on Windows, and can't be shared.  You must create a custom ReportPack, from the administration panel, and import your template in there (or create a new one). Then, from the roles page, like Gayatri pointed out, you can grant read only (or read-write) to your newly created template/ReportPack.  Other users will need to be a member of this new role (or use any existing one).  Remember that administrators (admin) users are full admin, and can't be restricted.
I can currently publish my reports under the tree however that can be modified by any user, but I would like to understand how to create a new read only node under ALL to publish my custom reports.
How can I Publish My Custom Reports under a Read Only Form