Yea, you will have to get it precisely right.
Go into your wireless settings, click your wireless signal's name (assuming you know it, on the card perhaps?), and then enter the password, precisely the same -- capitals, numbers, etc. All perfectly the same.
If your network doesn't appear in the list, then choose to add another network and enter your network's name perfectly (still remembering capitals etc.), following by choosing security (choose WEP or WPA, whichever it is), then click back and enter the password.