How to put WLAN card in promisc mode?

My WLAN card driver is ath9k and using CentOs 7. I used ifconfig wlp1s0 promisc to set it in promisc mode. When using tcpdump I am only able to see unicast traffic to my pc.

How can I set my card to promisc mode. ? And how can I confirm that the card is in pomisc mode, is there any flag which can display this. ?