The file location is only depending on the disc partition sizes, when you have enough space in the home folder, just put it there.
Before you can use the admin user for WinSCP you need to do the following in clish:
set user admin shell /bin/bash
copy the file to the machine
login with SSH to the machine, do an ls -l so you have the exact name of the file, go to clish
in clish use the following commands:
installer import local /home/admin/<uploaded file>
wait for it to finish and type:
installer install <Tab-Key>
you should see the file you have imported with 1 in front of it, now type 1 and hit enter.
It will now ask you if you are sure and want the reboot to happen at the end of the install.
Regards, Maarten