How do I erase everything on a lenovo laptop that doesn't have a disk drive?

The laptop isn't opening any programs because it keeps on saying that their is a malicious threat and when I try to uninstall the program that is causing the problem it won't let me. The laptop doesn't have a security protection and I can't download one because the threats won't let me surf the web. That's why I completely want to delete everything on the laptop I don't care if I lose all the programs.