I am assuming windows 10 is on the computer.....

First, use the Support Assist application on the computer to install latest Bluetooth drivers. Just Type Support Assist onto the search box, you should be able to see Support Assist application.

Dell SupportAssist Driver Update (Official Dell Tech Support) - YouTube

After, type Settings onto search box, select Devices, turn on Bluetooth switch. Please note you could also enable Bluetooth in the BIOS menu:

1. Power off computer

2. Power on computer, quickly start Tapping F2 key continuously until you see BIOS menu.