Here are the steps you need to follow to add a new column to your board:
Step 1. Click on the “Add” button
Note: If you can't see the "Add" button, this is because you aren't the creator of the board. Please, ask the board's creator to add the column.
Step 2. Choose the option “New column”
Final Step. Now enter your column’s name and click on the “Add” button to create a new column