There are a few different ways that you can password protect your Seagate external hard drive. One way is to encrypt the drive using software such as BitLocker or VeraCrypt. This will prevent anyone from being able to access the data on the drive unless they have the correct encryption key.
Another way to password protect your Seagate external hard drive is to set up a password for the BIOS or UEFI bootloader. This will require anyone who wants to boot from the drive to enter a password before they can even get into the operating system.
Finally, you can also physically lock the drive with a Kensington lock or similar device. This will prevent someone from being able to connect the drive to a computer without the proper key.
Whichever method you choose, make sure that you remember the password! If you forget it, you will not be able to access the data on your drive.