My central teeth are broken. What can I do to fix this?

See a dentist. Depending on the severity of the fracture, you can restore the teeth with something as simple as bonding. More complex fractures will requre crowns. See a local dentist for advice on what will work for your situation.
Options are: Tooth colored composite bonding, porcelain laminates or ceramic porcelain crowns are the three basic options. Which one is best depends upon many factors including but not limited to the amount of tooth lost, your particular occlusion (bite), how strong and esthetic you want the restorations to be, and naturally there is the cost factor. A personal exam & x-rays would be step #1.
See your dentist. No surprise, but there's no other way to fix them. Treatment depends on how severely they are broken. Bonding can repair many problems. Porcelain veneers (like a false fingernail) may be needed or even a crown (cap) that covers, protects, and disguises the problem. Done well, it will be impossible to tell. Be sure your dentist is experienced at "aesthetic" dentistry.