Hi and Welcome. My Name is ***** ***** I look forward to assisting you today with your question.
You don't need to charge it out of the box. Only charge it if it low on battery. Now just unplug it, then press and hold down the Power button for a few seconds and it will turn on. Then it will bring the setup screen. When asked to connect to WiFi network, select your WiFI network, enter your WiFi password ***** follow the onscreen instructions to connect.
Then it will ask you to register the device. So you can register it with your existing Amazon account which I assume you already have the credit card added, so you don't have to add again. But if it asked to add, then add it.
Here is the user guide if needed --> https://kindle.s3.amazonaws.com/Kindle_Fire_Users_Guide.pdf
The User guide is also available on the device itself. After setting up the device, follow the steps below to access the user guide;
If you have any questions or would like any additional information, please don't hesitate to ask.