FATAL: No bootable found! system halted. VirtualBox error

I finally finished the problem about virtual technology, so I tried to run the machine but then this popped up:

Did you make and install a Virtual Machine? Like Ubuntu? It does not look like it.

Get an ISO for a virtual machine you wish to run. Ubuntu is a good first choice .

Go to the Ubuntu site, download a current version of Ubuntu and save it.

Go to Virtual Box, open it, and make a new machine. Point to the ISO file you saved and follow the machine creation prompts.

Make sure you understand what Virtual Box will do.

If you think you already created a machine, make sure you know where it is and point Virtual Box to this machine.