The most important step here is to put your bluetooth devices into PAIRING MODE! Bluetooth devices can ONLY be FOUND and PAIRED in pairing mode.
IMPORTANT: Set your BLUETOOTH device to pairing mode.
If you don't know how to make it:
(1. Please refer to user manual of your BLUETOOTH device (headphones/mouse/keyboard etc.).
(2. Please simply Google brand+model+pairing mode (i.e. Bose QC35 pairing mode).
Once the device is in pairing mode, then your computer should be able to find it and connect to it.
Any more issues, pls contact firstname.lastname@example.org to book an online support.