add form fields to existing php web form

we have a pretty simple data entry web form for student summer Bible school. We need to add 3 or 4 additional choices to the form and database. The forms are in php and database is mysql I've attached a screen shot of the current form. We would like to add the option for student t-shirt Youth (Small, Medium, Large) Adult (Small, Medium) The choice should go just below the allergies... line for each student.