With a dropdown custom field, customers will be required to pick one of the options from a scroll-down menu.
1. Go to Settings>Customer Details
2. Go to the Custom fields tab
3. Click on the New field button
4. In the Type section, from the Type  scroll down menu, select the user picks one of the available choices
5. In the Application section, tick the customer making the booking  and/or to the participants  checkboxes to set when the field should be applied
6. In the Details section, input the Name  and Description  of the field.
7. Tick the Public  checkbox if customers can see this field.
8. From the Default  scroll down menu, select if you want to set a default choice or not
9. Click on the New choice  button to create a new choice for this custom field. A pop-up window will open.
10. Input the Name and Description of this choice.
11. Repeat for other choices.
Custom fields for participants will be asked during the booking process if you set that you want to Ask for the details of every participant: