If your computer does not have WiFi this is most likely because it is an older laptop or a desktop PC. Almost all modern-day laptops come with built-in WiFi, but it was just a perk up until about 5-years ago. Most desktop style computers don't come with built-in WiFi because the manufacturers figure that you aren't going to be moving it around too much.  But as we know, the manufactures are not always right.

So, you've been eyeballing that free WiFi hotspot across the street and now you want to hook-up to it from your house. To get started with WiFi you will need to get either a PCI WiFi Card (for desktop PC only) or a USB WiFi adapter (for desktop or laptop).
 

PCI WiFi Card

Most any 802.11b or 802.11g PCI card will work to get connected. Installation requires opening up your computer (desktop PC) and inserting the card into one of the available slots. The card will come with an antenna that fits onto the card and protrudes out from the back of your computer (where all the connectors are located). This is not always the best setup for WiFi because the antenna is partially blocked by the computer case itself. Remember that WiFi signals do not go through metal. Also, the antenna on the PCI card is limited to the same location as the computer. If your computer is not in an ideal location for receiving WiFi, then you're stuck with bad signal until you move your computer to a better location.
 

USB WiFi Adapters

A better solution for getting better WiFi is to get a USB WiFi adapter. Installation is easy; just install the software and plug it into the USB port on the back of your computer. I don't recommend using the USB ports on the front of your computer as they have limited power output in some cases. This is because the are designed for low power devices like your keyboard and mouse.

Some USB WiFi adapters (like this one ) have an extra 15' of cable so that you can put it in a better location for receiving WiFi (like a window). Your WiFi signal strength will be stronger or "faster" if you can eliminate obstructions such as walls, furniture, metal shelves, etc by placing your antenna in a better location. Another great thing about USB WiFi adapters is that they can be use with laptops to get more WiFi reception then the built-in one.
 

Connecting to a WiFi Hotspot

Once the WiFi card or adapter is installed correctly, you can try to connect to the hotspot. Using the supplied software program that came with your WiFi card or adapter, you can "sniff" the air waves for nearby WiFi hotspots. The results will be displayed and you can choose to connect to any non-password protected site of your choice. Once connected, you will have WiFi internet. If the WiFi hotspot requires a password then you will not be able to use it, unless you can find the owners of the hotspot and request their password. In this case it will be best to persuade them with a hot apple pie or an agreement to pay for half of their bill, because they won't give it away easily.