To manage the event's registration options, go to the Event's registration options page.

You can edit the existing questions, or you can add a new one by clicking on "Add new".  

Input the following data: 

Question, the registration question where this option will be rendered (needs to be already created); 

Display, the text that will be shown for this option; 

Price, the price that this option will add to the registration fee (if 0, it will not be shown); 

Max available, the maximum number of signups with this option (if 0, there will be no limit); 

Order, inside a registration question, it's options will be rendered ordered by this value. 

Here's an example of a Single choice question: 

Here's an example of a Multiple choice question: