Open your browser and visit RapidAPI.

If you don't have an account, click on Sign Up in the top-right corner of the page.

You can sign up using Google, GitHub, or your email. If you already have an account, just click Log In and enter your credentials.

Once logged in, use the search bar at the top of the page to find the API you want to use.

For example, type in "weather" to see APIs related to weather data.

Click on the API you are interested in. This will take you to the API documentation page.

Look for the Pricing tab and choose the plan that best fits your needs. Many APIs have a free tier for testing purposes.

Click Subscribe under the plan you want.

After subscribing to the API, you will see your API Key in the "Endpoints" tab of the API page.

The key will be listed under the "X-RapidAPI-Key" field in the request example. Copy this key for later use in your app or project.

You can test the API right from the RapidAPI platform by going to the Endpoints tab.

Choose an endpoint, fill in any required parameters, and hit the Test Endpoint button to see a response.

Now, you can integrate the API into your project by passing your X-RapidAPI-Key in the headers of your HTTP requests.