Connecting your computer to WiFi network created by your WiFi router
Mac OS X
On your Mac computer click on WiFi antenna logo in menu bar (at the top right corner of the screen) and select your network from the drop-down menu:
(if you don't see the WiFi antenna logo in menu bar, you may want to run the System Preferences app, open the Network tab, select your wireless adapter there and find an option to show your WiFi adapter status in menu bar)
Enter your network's password and click OK. It is very important to ensure that you're entering the password correctly, because sometimes, if the password is incorrect, it may look like you're connected to a network, but no actual file transfer will happen.