Go to your searchbar and type "Making a wireless connection secure", or
"Secure your wireless connection" or anything else similar. You will have an
abundance of results.
much of the security is configured on the wireless router. The whole idea is
to use encryption to encrypt the data sent between the computer and the
wireless access point. Recomended will be WPA2. For more information on how
to configure your wireless AP/Router, you will need to consult the product
manual or contact the vendor.