How to subscribe to an IMAP folder with Thunderbird

Step 1: Select the mail account from the left column.

Step 2: Right-click on your mail account name and select the Subscribe… option.

Step 3: You will see all the available IMAP folders on the server. Select the ones that you want to add to your mail client and click the Subscribe button.

Step 4: Press the OK button and you will notice that the new folders are now available.