Your Raspberry Pi 5 needs a few other parts to get it up and running - consider it a motherboard rather than a ready-to-go computer.
For a full Raspberry Pi 5 desktop setup, you will also need the following items (many of us have spare keyboards and MicroSD cards, so you may not need all of these):
- A MicroSD card (at least 32GB)
- USB-C 5V 5A power supply
- Micro-HDMI cable
- Keyboard/mouse
- Monitor
You may also want to consider grabbing a case to protect and cool your new board.