I bought lenovo All in One Pc without OS and when i turn my pc on i only see white screen?

Yes…

So?

That's what you get with no OS.
You have to add one yourself.

My question is, am i going to get the bios menu when i'm going to plug in a keyboard?

Not sure on your knowledge so apologies in advance. No OS means that there's no operating system installed on the machine. The operating system is the software that loads up when a computer is turned on. Examples of operating systems include. Windows, Mac OS, Linux, Chrome etc. You will need to purchase an operating system and install it onto your all in one PC. If you're not sure on how to do this, take it down to your local computer store and ask for help. This isn't a complex process.

Hope this helps, let us know how you get on

Install an OS

With no OS, the computer doesn't know what to do.

You need to install an OS, such as Windows or Linux.

You _should_ see at least the BIOS startup messages, complaining about not finding a bootable OS.

Read the manual or contact the dealer.

Try buying a disc with Windows or whatever on it and then turning the PC on