"No bootable device available!!!" error when installing new SSD

My PC originally had an HDD, but it was bad, so I got a Crucial BX550 1TB 2.5in SATA SSD. I got a flash drive beforehand because I knew I would have to install Windows 10. When I plugged in the SSD and the flash drive, it showed an error that I forgot. I changed a setting in BIOS, and I got to the "No bootable device available!!!" error. Any idea how to fix it?