You can't delete meeting in Tadum. Individual meeting minutes for each meeting are saved as read-only and cannot be deleted. You will find the minutes listed in the left sidebar. After a few meetings within a rhythm, we hide the older meetings, so the sidebar column doesn't get too long.
If you are the person who created a meeting rhythm, you can archive that rhythm by clicking on the 3 dots next to the Meeting Rhythm title, and clicking Archive.
If you did not create the meeting rhythm, you cannot archive it.