Google Groups

My OS is win 10 pro 64 bit and I am a moderator in a google group called dcsankirtan.  Whenever I create a new topic, which is usually an announcement, I would like to insert a link to another topic that I created a few days ago.  Typically the topic is an announcement of an Event.  Rather than repeating the details like the location and other details, which will make the announcement lengthy, thus my aim to provide a link to another topic which will contain this announcement.  Can this be done, and if Yes, how is it done.  Thank u.