I'm assuming you know for a fact it has a bluetooth adapter. If it doesn’t, you need to buy one.
Assuming it does, check device manager and verify the device is there and the driver is installed. If it's not listed at all, then either you don't have a bluetooth adapter, or perhaps it's been disabled in the BIOS (in which case, enable it on boot-up, usually need to ht F2 or Del key to enter BIOS). If it is listed, but it has a yellow exclamation mark next to it, it means either the drivers have not been installed, or is misconfigured in some fashion. In either case, correct the problem by properly installing the drivers.
To access device manager, hit Windows key + R, type "devmgmt.msc" (no quotes) and hit enter.