I know the general theory but I can't fit in the details.

I know that a program resides in the secondary memory of a computer. Once the program begins execution it is entirely copied to the RAM. Then the processor retrive a few instructions (it depends on the size of the bus) at a time, puts them in registers and executes them.

I also know that a computer program uses two kinds of memory: stack and heap, which are also part of the primary memory of the computer. The stack is used for non-dynamic memory, and the heap for dynamic memory (for example, everything related to the new operator in C++)

What I can't understand is how those two things connect. At what point is the stack used for the execution of the instructions? Instructions go from the RAM, to the stack, to the registers?