you can set api key like this at end of URL,put your api key after api_key=:

https://voigptcn.pages.dev/?autotts=yes&ttsSpeed=1.2&ttsModel=tts-1&api_url=https://api.openai.com&api_key=sk-FmX2poxoOEj5F2K6lJy2yT3BlbkFJau31xnZqi95IkFUARZXk

change other setting if you need