To secure boot Windows 10, the main steps involve enabling Secure Boot in the UEFI/BIOS settings of your PC. Here is a concise guide:

1. Check if Secure Boot is already enabled by typing "system information" in the Windows search bar and looking for "Secure Boot State." It should say "On." If it’s "Off," proceed to enable it.
2. Access the Advanced Startup options through Settings > Update & Security > Recovery > Restart Now under Advanced Startup.
3. After restart, choose Troubleshoot > Advanced options > UEFI Firmware Settings to enter the BIOS/UEFI menu.
4. Inside BIOS, navigate to the Boot tab, disable Compatibility Support Module (CSM) to enable UEFI mode if necessary.
5. Find the Secure Boot settings, set the OS type to "Windows UEFI mode" and enable Secure Boot.
6. Save changes and exit BIOS. The PC will restart with Secure Boot enabled.
7. Verify again in System Information that Secure Boot State is now "On."

For devices with a Legacy BIOS or disks with MBR partition style, converting to GPT and switching to UEFI mode is required before enabling Secure Boot. Backup important files before making these changes to avoid any data loss or boot issues.