How Do i Timestamp everytime a label is added or removed?

[Stanford Siu]

I am trying to simply to name the label "Completed" or "Mailed out" or "waiting for Owner approval"

It seems to be a simple feature, but I don't seem to know how to "turn it on"

Thank you

[Crystal Davis]

HI Stanford, 

Crystal from Trello Support here! 

You can edit labels to show words by clicking on the pencil icon next to the label in the menu. From there you can edit the name! Here's more information on how to do that: https://help.trello.com/article/785-editing-labels-on-a-board