Measure the space where you want to affix a neon light, using a measuring tape. Check the measurements against the size of the neon light you wish to purchase online. Measurements are usually given in inches and and found by the neon light's product name.
Contact a company that sells neon lights, such as Neon Design a Sign, I Love Neon or Neon Sign World. Most of them have online stores from where you can order neon lights. These companies sell ready-made neon lights of all colors and sizes, and some sell personalized designs. Browse the company's website and choose one of the lights.
Visit the company's website and choose a neon light design. Click on the sign and click "Add to My Shopping Cart." Click "Check Out," fill in your details, your address, phone number, the 16-digit number on the front of your credit card, the card's expiration date and the three-digit security code from the back of the card.
Click the "Check Out Now" button to finalize the payment.