Canned Responses Pro shows up in Jira every time you're about to make a comment, edit the description of an issue or any Text Field (multi-line) custom field. It also integrates with other popular plugins such as:
JEditor - Rich Text Editor for Jira
Select template from the Canned response dropdown placed right above the field you're working on (e.g. Comment).
Just start typing $ and the macro name to get suggestions.