You need to use std::vector::push_back()
instead:
while(cin >> x)
myVector.push_back(x);
// ^^^^^^^^^
and not std::vector::insert()
, which, as you can see in the link, needs an iterator to indicate the position where you want to insert the element.
Also, as what @Joel has commented, you should remove the parentheses in your vector variable’s definition.
std::vector<float> myVector;
and not
std::vector<float> myVector();
By doing the latter, you run into C++’s Most Vexing Parse problem.