How to install windows 7 on y510p?

Hi, I have this new Lenovo y510p and it came with a Windows 8 SL and it's damn slow and I think many of my games are misbehaving so I tried to install win 7 but when I reach the screen where it asks where to install win 7 and I tried to select a partition but for every partition it Is saying windows can't be installed here it is of gpt style partition I tried to format and deleted the portion and tried to install on a unallocated memory but no change same message so I tried to read about it and they are saying some uefi and stuff and I'm not understanding so please tell me a direct procedure to install win 7 on this laptop.