Open Teamspeak which is downloadable from the internet via ADSL, EDGE, 3G, dial up or what ever way you use. Just do a search on google. Ok I will post the link

http://www.goteamspeak.com/?page=downloads

Install the file you have downloaded. Start teamspeak,
Click on connection
Then click on connect
Right click on servers
Click on add server
Name the server whatever you like to call it (give it your dogs name for all I care, Revenga, you can give it your cats name)
Add all the parameters that follows bellow

Server Address; gahena.saix.net:8767
Nickname; Your_Nick
Do not tick "Allow server to assign a nickname"
Select "Anonymous"
Server Password; dark
Select "Auto reconnect"
Default Channel; COD4-dBx2
Default Subchannel; leave open
Channel Password; dark

Then say connect

Plug in your mic (check this, trust me on this one, I get to work with people everyday complaining about things that doesn't work then it not plugged in)

In the "Settings" tab, select "Sound Input/Output Settings"
Adjust your output volume the way you like it
Choose wether you want "Push to talk" or "Voice Activation"

If you choose "Push to talk" assign a key by clicking on "Set"

If you choose "Voice activation" adjust your "Voice Activation Level"

Click on close.

This is a step by step guide(I can't add any more steps, well I can if I want to but I don't want to), if you follow it, it MUST work.