I bought a lap top and trying to use my home Wi-Fi and it as for security key

It's asking for the password for your Wifi? Your Wifi network shouldn't be "open" (ie you need a password to access).

Unless you configured it and changed the password (which is recommended), the 'stock' password should be on a sticker somewhere on your router.
 
MERGED QUESTION
Question from tonyas701 : "Tried to hookup to my hot spot on my phone it also ask for security key"



Please keep it to one thread:
http://www.tomshardware.com/answers/id-3636083/bought-lap-top-home-security-key.html

You'll need a key either way. Using the hotspot on your phone, when enabling it on your phone - it'll show you the key.