Computers that do not have an internal Wi-Fi antenna will need an external Wi-Fi antenna in order to connect to a wireless network locally. Without this antenna, the computer user will have to connect their computer to a modem, using a network cable, in order to access the Internet. If your computer doesn't have an internal Wi-Fi antenna and you are needing to add an external Wi-Fi antenna to your computer, you can do so without being a computer expert.
Locate a USB port on your computer and plug in the external Wi-Fi antenna into it. The USB port is rectangular in shape and generally located on the back of the computer's tower or on the side if the computer is a laptop.
Download the external Wi-Fi antenna's software onto the computer. You will need to put the CD-ROM that came with the external Wi-Fi antenna, into the CD-ROM drive and follow the instructions that appear on the computer's screen.
Check for an Internet connection by finding the wireless icon that is located at the bottom right of the computer screen that looks like a computer. Your computer is not connected to the Internet if there is a red "X" on top of the icon. If you see a red "X", right click on it and click on the word "configure" that appears in the pop-up box to configure your computer so you can connect to the Internet.
Your computer should automatically connect to the Internet once you have added the external Wi-Fi antenna and downloaded the software. If it does not and you try to configure it by right clicking on the red "X" and cannot, you will have to do so manually by following the instruction booklet that came with the external Wi-Fi antenna.