How to switch on Bluetooth in Windows 7, 8.1 or 10?
Press Fn+F5 (or F5). Lenovo Wireless Device Settings window will show. If it fails to display, it may due to that energy management has not been installed correctly. Check Why "Lenovo Wireless Device Settings" window not show after pressing "FN+F5" to troubleshoot.
Method 2 (Applicable for PCs):
1. Click Start --> Devices and Printers
2. Right-click your computer in the list of devices and select Bluetooth settings.
3. Select the Allow Bluetooth devices to find this computer checkbox in the Bluetooth Settings window, and then click OK.
4. To pair the device, go to Start --> Devices and Printers --> Add a device.
If your product is ThinkPad, please check this document "How to turn on or off Bluetooth – ThinkPad".