How to add User Text Editor interactive to website

please help…I don’t even know what it is called that I am looking for or how to go about creating it…

I am a screen printer, tee shirt images that are customized with the customer’s name, ect.

I have graphic images in the background. These graphics have text. I am looking for the means to allow the user to edit their text fields and display it on screen. There are dozen of websites that have this capability, but I don’t know what it is or called or how to start researching.

~melanie

let me define a little better…Users would have the option to select and adjust text, fonts, and other effects to be applied within the printable defined area.

Does anyone know where to start or find applications that do this.