Example:
aireplay-ng -0 5 -c 66:77:88:99:00:11 -a 00:11:22:33:44:55 wlan0
obviously your station number and bssid number should be different.
Now if you have done this all correctly, you should receive a handshake agreement
(check you first terminal it should be on the right hand corner indicating "WPA handshaking: (with the victims bssid)".Now type;
dir




and find locate the file, for me the file should be example-01.cap.now type;
aircrack-ng example-01.cap -w /pentest/wireless/aircracck-ng/test/password.lst
Now obviously the backtrack password list is very small,
so you can do a couple of things you can add your own password list ( which is good if you want to test you own wifi)
you can download password list from the wordlist forum