1. Click Wifi Icon. 


2. Click Open Network Preferences. 


3. Click Advanced.


4. Select your Wifi.


5.  Click (-) sign to remove network on your network list. 


6. Click (+) to add network on your network list.


7. Click Show Networks.


8. Select your network.


9. Click Join.


10. Type your SSID password. 


11. Click Ok.


12. Click Ok. 


13. Click Apply.