If you have not sold any tickets for the ticket type you would like to delete, then you will be able to delete that ticket type. To get started, go into your Event Home and then click the Details tab.
Click on the black and white "X" next to the ticket type you need to delete. A prompt will open up, and ask "Are you sure?" If you are, click "yes." However, if you've made a mistake and clicked the wrong "X", you can still say "no", and delete a different ticket type.
If the "X" is grayed out, then you will not be able to delete that ticket type, as a ticket has been sold at that price point. What you can do is change the visibility of the ticket type to Nowhere in order to disable sales for that particular ticket type.