Question

I got a new computer about 4-5 months ago and I go on YouTube and search up how to downgrade windows 10 to windows 7 but you need Local Disc (C:) to do it but you only have that if only you upgraded it. I bought the computer after Windows 10 came out so I can't have that option to do it with Local Disc (C:) I have been trying to search everywhere on google but it doesn't have no results but "how to downgrade with Local Disc (C:)" (doesn't literally say that) But yeah, I really need help and want to downgrade to windows 7 immediately. Please help!