OpenAI has yet to make GPT-4's visual input capabilities available through any platform because the research company is collaborating with a single partner to start. However, there are ways to access GPT-4's text input capability.
The only way to access the text-input capability through OpenAI is with a subscription to ChatGPT Plus, which guarantees subscribers access to the language model at the price of $20 a month. However, even through this subscription, there will be a user cap which means you may not be able to access it whenever you'd like, something to consider before making the investment.
There is a free way to access GPT-4's text capability and it's by using Bing Chat.
Also: Still waiting for Bing Chat access? Make sure you do these 4 things
The day that GPT-4 was unveiled by OpenAI, Microsoft shared that its own chatbot, Bing Chat, had been running on GPT-4 since its launch five weeks ago. Bing Chat is free to use but does require signing up via a waitlist.