Here is how to add card mirror & card sync in trello
- First click on the "Boards" item in the left sidebar
- Then click a board in the workspace section
- Next click on the menu icon (three dots) in the top-right corner of the board
- Scroll down in the menu settings
- Click on the "Power-Ups" button in the dropdown menu
- Select the "Automation" category in the left sidebar of the Power-Ups window
- Click on "Add" button next to the "Card Mirror & Card Sync (2-Way)" power-up
- Finally click the "Add" button in the confirmation dialog to install the power-up



