Passing data through a void function

[heew]

Hey, first time posting here. I am new to C++ (day 2 since I started learning it) so bear with me.

Ok so my question is if I were to pass some data or values from the main() function through a void function (which main purpose is to display the data in a certain manner); how should one go about doing so?

For instance:

// example.cpp -- poorly written, just trying to learn
#include <iostream>

void format()
{
       using namespace std;
       cout << "Time: " << min << hrs << endl;
};

int main()
{
      using namespace std;
      int hrs;
      cin hrs;
      cin min;
      format();   // call the void format to display them in a certain way
      return 0;
}

Obviously this is really poorly written, and confusing for the user. My main goal is to learn how to pass through values to a void function.

Also a bit off-topic, but is there a downside to place "using namespace std;" outside a function say if out of 100 functions only 10 of them use it? Would it make the program slower/unstable in any way or is this something one could do without any downsides?

Please excuse my English if it is hard to understand - it's not my mother tongue.

- Heew