How do I reinstall Android, LineageOS etc?

Previously, I rebooted Android, unlocked the bootloader, flashed and installed LineageOS. After that, I locked the bootloader, but everything was reset. OS also disappeared. If you turn on the power to start, the circle of LineageOS eyes will keep rolling and nothing will move. Also, when you unlock the bootloader, nothing happens, only the “Google” character floats. How can I add LineageOS from here? There were no LineageOS files in the recovry mode install folder. The smartphone does not have the ability to install files from a browser. Can I send files from my PC? Or can you install from PC?

Why?