The built-in Bluetooth Integration app allows you to add compatible BLE (Bluetooth Low Energy) devices to your hub. This integration requires hub model C-8 Pro.
From the sidebar of your hub, navigate to Integrations and select Add Integration or Add Built-In Integration:

Select Bluetooth Integration from the list of built-in apps.
If this is the first time you have ever installed this app on your hub, you may be prompted to install dependencies; follow the prompts to continue, or continue to the next step if you do not see this prompt.
After installation of the app or dependencies, you should see text towards the top of the app saying Integration is running. If you see "not running" instead, wait a few minutes (particularly if you are starting the app for the first time after installing dependencies) or refresh the page. Please note that this integration is currently in beta. If you continue to have problems, please visit https://community.hubitat.com for discussion.
You may also see a suggestion to add the Bluetooth Integration app on the home page if compatible devices are detected in range of the hub. Adding the app either way will produce the same results.
The main page of the app will list discovered devices and add them to your hub if selected, following the prompts. (Compatible Bluetooth devices must be added via this integration app, not from the Add Device page.)
If you see No devices found, ensure the devices are within range of your hub, and try waiting a few minutes, depending on the activity of your devices (the app listens for compatible device packets and can only "see" within Bluetooth range).
Only select Bluetooth devices are compatible with this integration. At the moment, the integration supports BTHome V2 format devices, with popular off-the-shelf products including most Shelly Bluetooth devices but also many DIY devices (although as with any device, a compatible driver is required; see the List of Compatible Devices for built-in options). Additional device types will be explored for future platform versions.