Click on the "Branded Fares" option in the button panel, located to the right of the flights (option 2 in the image below).
Once you have selected the "Branded Fares" option, a new window will appear showing the different available branded fares (e.g., Light, Plus, Top). In this new window, you can view the prices and features of each branded fare. Choose the option you want by clicking on "Select."
To verify that the selection has been applied correctly, check that the price has been updated to reflect your selection and ensure that the "Branded Fares" button has a green checkmark, as shown in the following image.
If you wish to undo the selection, simply click the red cross on the "Branded Fares" button. This action will revert the price to its original amount, without any branded fare applied.