Hi @Tobias kjeldsen,
Simply replace the laptop’s existing WLAN card (if there is one) with a WLAN + BT card (supplier example only). The Lenovo part number for the module is 04X6008. Search online using the part number only to get suppliers that may suit you better.
It may be that the card that you can salvage from another laptop is a WiFi (WLAN) + BT module and hopefully it is compatible with the laptop.
Here’s the hardware maintenance manual for your laptop.
Go to p.65 to view the necessary pre-requisite steps and then the procedure to remove/replace the WLAN card.