Declare a pointer by putting an asterisk after the type: int* ptr declares a pointer to an integer. The asterisk tells the compiler this variable holds an address, not a direct value.
To make it point somewhere, assign an address using &: int x = 5; int* ptr = &x;. Now ptr holds the address of x. Types must match: you cannot point an int* at a double variable. I recommend int* style because it emphasizes the type.
You are declaring a variable of type "pointer to int". This clarity helps when reading code.