If by accident on my apple computer you deleted my photo booth how do i get it back?

Many ways to fix this. Open the trash can and drag it out. If you emptied the trash go to finder and search Photo Booth. If you are using Time Machine then you will have it on the external hard drive. If you have the original install disk just insert it and just click the Optional Installs option. Click continue and then choose Applications and then check Photo Booth. Click continue and it will reinstall Photo Booth.