How do I push items to a Stack<T> after creating a Stack<T> instance in code?

Question

I am creating a Stack<T> where I have the type of the Stack in a variable. After I have created the Stack<T>, I am wanting to push items to the Stack. How can I access the Push method?

Here is my code:

var itemType = GetIEnumerableItemType(type);
var stackType = typeof(Stack<>);
var constructedStackType = stackType.MakeGenericType(itemType);
var instance = Activator.CreateInstance(constructedStackType);

EDIT

Here is some code that I have tried that works with a List<T>:

var itemType = GetIEnumerableItemType(type);
var listType = typeof(List<>);
var constructedListType = listType.MakeGenericType(itemType);
var instance = (IList)Activator.CreateInstance(constructedListType);
//instance.Add("example item");

Thank you