Here's how you turn wifi on and off on your playbook: http://helpblog.blackberry.com/2012/08/turn-wi-fi-on-off/
If it is on and you can see the wifi network you want to connect to, but still cannot connect. You need to contact the owner of the wireless network and have them provide you with their wireless password or passphrase.
Answers & Comments
Here's how you turn wifi on and off on your playbook:
http://helpblog.blackberry.com/2012/08/turn-wi-fi-on-off/
If it is on and you can see the wifi network you want to connect to, but still cannot connect. You need to contact the owner of the wireless network and have them provide you with their wireless password or passphrase.
I hope this helps.