Deauthing a network means to forcibly disconnect all the devices connected to a network. This is possible as the Management frames used to administrate a WiFi connection are unencrypted. So a 3rd party can inject false Management Frames into a network, disconnecting clients.
Deauthing should not be confused with signal jamming. Think of jamming as shouting at the top of your voice to stop two people having a conversation. Deauthing is like putting on a fake moustache and bad accent, pretending to be one of the two people, and then just ending the conversation.
SCAN > SCAN APs
SELECT > APs > Network_SSID
ATTACK > DEAUTH, START
Instead of scanning for APs, scan for stations. Station refers to a WiFi device connected to an access point. Scanning for stations will take 15 seconds, you cannot use the device whilst scanning. You may lose connection to the deauther’s WiFi hotspot whilst scanning.
Select a station like you would an AP, then just deauth as normal.