Good question! You might want to boot though the UEFI/BIOS Settings (Which is smashing a specific button during the boot processes. Which differs unfortunately for every motherboard brand. Usually the button is displayed for a few seconds on the screen slightly after you press the ON button).
In there I recommend configuring the boot order to start your SSD first. Once you boot I recommend to wipe your current HDD because I suspect that there is still a bootloader in there