AFAIK you don't run C commands, C is a compiled language, not interpreted. You can create a simple C program in a text file and run something like gcc textfile.c (here textfile.c is the C language text file). It will output to an executable called a.out. In UNIX/Linux you have to alter files permissions to execute them so you can type something like "chmod 777 a.out" to make the file executable. then you can type "./a.out" to run the executable file in UNIX/Linux.
Stacks are one of the most basic data structures, where OS's use them to keep track of what memory address a program has "jumped from". Otherwise we'd have to use goto's, which suck.
From what I am reading so far with Linux, it already has tools to run C. So I'm guessing the 'mingw' install is not going to be necessary? I already have it installed on my Win10 system, but not on the VM.
Without seeing it yet, I am speculating the first lab is about stack overflow where some malware is introduced in the stack and the buffer is exceeded causing it to push back to the malware. Am I making any sense with that? Anyway, with any computing, practice and repetition is the only thing that works. I am hoping that 'C' will bring up memories of BASIC programming back when I was a young teenager.