Classic Healing Assignments (CHA) let you assign Healers in a raid to Tanks or Raid markers, and post the assignments in the Raid channel (or a healer channel if you like).
Open the CHA user interface by left-clicking on the CHA minimap icon.
You can now create a new Template, and add wanted tank(s) plus healer(s).
See a Template as a Boss fight: one template for one boss.
For example: Lucifron might require 3 tanks, so you'll make a template with 3 tanks, each having one healer assigned.
Ragnaros might only require one tank, but you also need Melee healers, so in this case you will add two tanks: one main tank, and one Custom tank you can name "Melee".
When your assignments are ready, you can right-click the minimap icon to post the assignments to Raid chat.
This addon is a port of Vanilla Healing Assignments, originally made by Renew @ Vanillagaming.org