Installing Linux Mint alongside windows - disk management help?

Okay I'm finally doing the thing but I want to hang on to my windows install until I'm fully ready to switch.

The situation: System has two hard drives, 256 GB windows drive (installer calls this /dev/nvme0) and 500 GB SSD (/dev/sda).

I shrunk the partition on the SDA and planned to transfer the files I have on there to the Linux partition, then grow the Linux partition to the whole drive.

The problem: I am not fluent enough to communicate my wishes to the installer: I'm assuming I need to turn the free space into the new Linux partition but I am not sure how to answer the prompt for a mount point and also don't know what to put for the "device for boot loader installation" drop-down