I'm not really sure if I understand what you are asking. Anyway, I hope this helps:
// A Vector2i stores two ints.
sf::Vector2i myVector(10,10); // Declares a vector with 10 and 10.
sf::Vector2i myOtherVector; // Declares a vector without specifying values (so it will be 0 and 0 by default)
myVector.x = 20; // Changes the first value of the first vector.
myVector.y = 30; // Idem, but for the second value.
myOtherVector = sf::Vector2i(2,3); // Another way of changing values. Now the second vector is 2 and 3 instead of 0 and 0.
std::cout << myVector.x << " " << myVector.y << "\n"; // Prints both values of the first vector (20 and 30)