If you are still not able to get online, make sure that your computer has joined the correct Wi-Fi network.

Your Wi-Fi network should be listed in the Wi-Fi menu. The Wi-Fi network with which your Mac is associated will be checked, as shown below:

Select your network if it is not chosen. If your Wi-Fi network is secured using a password, you will be prompted to enter a password as shown below.

Note: If you do not know your network password, you will need to contact the administrator of your Wi-Fi network. If you are the administrator/owner of the network, you may need to configure your router in order to define the password for the network.

Your Wi-Fi network may not be visible in the list. If the network is closed, it will not broadcast its network name. In order to join the Wi-Fi network, choose Join Other Network from the Wi-Fi menu. You will be prompted for the network name and security setting.

Enter the name of your network and choose the Security your network uses.

If your network is still not visible in your Wi-Fi network list, then it may be using an incompatible Wi-Fi standard. Most Macs support all common Wi-Fi standards. To check which standards your Mac supports, use Network Utility. Set the network interface to Wi-Fi and examine the information listed after "Model:"