If your motherboard doesn't support bluetooth then there is nothing you can do to get it to support it. However bluetooth has been around awhile so if your computer is less than 10 years old then it is probably there, just not enabled.
In Windows search for "Bluetooth". In the settings, if it comes up, turn on bluetooth. That may be all you need to do. If you don't see the option at all then make sure it is turned on in the BIOS (some boards have this option). The easiest thing to do is google for your motherboard specs and see what they say.
If for some reason your MB doesn't support bluetooth then the only other option is to get an adapter. There are adapters for USB (and probably PCI) that you can use to provide bluetooth support for computers that don't natively support it.