Installed Kali, can't boot Windows 7 now

I'm a newbie, but I thought I couldn't **** up if I followed all the steps, this is also why I haven't backed up any data and in hindsight that was foolish of me. Maybe I've missed something. When I start the PC it automatically goes to Linux and doesn't give me the option to switch to Windows. In the BIOS menu I don't see any Windows booting option, on Linux I try to run update-grub but it doesn't work. What can I do guys, I'm kinda panicking here. Am I supposed to use grub as a boot loader? How do I do that?