Hi,
If you only have Wifi available on your laptop, you may be able to replace the existing WLAN card with a combined WLAN + BT card [https://www.parts-people.com/index.php?action=item&id=12371|example only] - (there is a link on the page for the appropriate drivers).
Here’s a link to the [http://topics-cdn.dell.com/pdf/latitude-e6540-laptop_owners-manual_en-us.pdf|owner manual] for the laptop.
Scroll to p.19 to view the necessary pre-requisite steps and then the procedure to remove/replace the WLAN card.