Can't detect or enable the wifi in ubuntu 14.04

Question

This is my first time to using ubuntu. I am unable to access the wifi, even if I enable it. I can access internet from the wired connection. This is my laptop detail:

Output of nmcli nm:

RUNNING         STATE           WIFI-HARDWARE   WIFI       WWAN-HARDWARE   WWAN      
running         connected       enabled         disabled   enabled         enabled   

and my specs:

 *-network
                description: Ethernet interface
                product: QCA8171 Gigabit Ethernet
                vendor: Qualcomm Atheros
                physical id: 0
                bus info: pci@0000:04:00.0
                logical name: eth0
                version: 10
                serial: 74:d0:2b:c4:54:14
                size: 100Mbit/s
                capacity: 1Gbit/s
                width: 64 bits
                clock: 33MHz
                capabilities: bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation
                configuration: autonegotiation=on broadcast=yes driver=alx duplex=half ip=10.9.76.61 latency=0 link=yes multicast=yes port=twisted pair speed=100Mbit/s

What should I do?

Thank you in advance.