Secure boot password question, installing Mint 20.1 alongside Win 10

I am trying to install Mint 20.1 alongside Win 10 and when I get to the screen that asks if I want to connect to the internet for install of multimedia codecs, and also asks to create a secure boot password I am confused.
The BIOS has a password already, and I am not sure if this is where I put my Linux password, or if this is going to be yet another password.
I am hoping the install works, as the laptop (Toshiba Qosimo X70-A) has two SSD drives installed internally.
Also, I want to set the computer so it always boots to Linux first as I rarely need to use Win 10.

See Q4 & Q5

Follow the guide you choose, very thoroughly, step by step. Doing this should minimise the issues you may experience.

A secure boot password is optional.

I haven’t installed Mint in a dual-boot system but a dual-boot of Ubuntu (upon which Mint is based) will set up the GRUB screen so that Ubuntu is both the first choice and the default choice when booting.