It's actually quite simple to do
How to Connect a Bluetooth Mouse to a Chromebook
Switching to a wireless mouse can improve your productivity if your Chromebook has a terrible or slow trackpad. Additionally, external mice are also more ergonomic and comfortable. This tutorial will highlight ways to connect a wireless mouse to your Chromebook.
We've also included solutions to issues you may encounter when connecting a wireless mouse to your Chromebook.
Wireless mice with a USB receiver/connector or Radio Frequency (RF) dongle have a plug-and-use setup. The USB dongle transmits signals from the mouse to your Chromebook.