If you're installing wifi.tz via Apps use OnBoot install option then use the wifi icon on the wbar (usually at bottom of screen) to launch it.
Or, in the terminal, type: wifi.sh (because wifi.tcz is an extension containing the script "wifi.sh")
The basics:
First, you'll need to download an extension and all it's dependencies (normally accomplished with Apps)
Next, you'll need to load the main extension which in turn loads any required dependencies if not already loaded, use Apps or tc-load -i )
lastly, you'll need to Launch the main application (use the application icon, menu item or simply type it's name in the terminal and press enter)
If already downloaded then you might need to load the extension. You can use "Apps > Load App Locally" to accomplish this or from the terminal enter this command:
tce-load -i wifi
to load wifi.tcz and all it's dependencies, then sudo wifi.sh
to launch it with root privileges
note: In most cases typing the extension name without the .tcz will usually help