Using Ubuntu from Oracle VirtualBox

I am completely new to this forum. I would like to ask if anyone knows how to solve this problem. I want to use Ubuntu from VirtualBox. The “Oracle VM VirtualBox Manager” has four tabs: New, Settings, Discard, Show. When you click on New, a window pops up and you are asked to name your operating system. I named it Ubuntu. Below the box where you named your system, there are two drop-down menus: Type, and Version. For Type, you choose Linux, of course. But for Version, the drop-down menu has choices like Arch Linux (32 bit), Debian (32 bit), Gentoo (32 bit), Mandriva (32 bit), Ubuntu (32 bit), Other Linux (32 bit). But THAT is my problem. I need an option for Ubuntu (64 bit) and that option is not in the drop-down menu! Any suggestions about how to overcome this problem, please? Because there is no option for 64-bit, I keep getting (on VirtualBox) the message THIS KERNEL REQUIRES AN x86-64 CPU, BUT ONLY DETECTED AN i686 CPU.

I’ve moved this to the category because this site isn’t designed to take tech support questions. Sorry. I’d recommend using one of the official support channels listed on the page.