Actually, the methods you are likely to call on the RenderWindow in your render method are likely going to be Draw, and Display, both of which are not const methods. Thus, you should not pass a reference to const, but just a reference, as a reference to const will not allow you to call any methods that are not const-qualified.
Use
void render(sf::RenderWindow& Window);
basically any time you want to pass a non-integral type (not an int, float, etc) for example (std::vector, sf::RenderWindow, sf::Texture, etc), you should be passing by reference, not by copy. When you write
void someMethod(sf::Texture Texture);
you are copying ALL of the data that is held in the instance you are passing as a parameter, and you should opt to pass by reference
void someMethod(sf::Texture& Texture);
However, passing by reference allows you to change the original object that was passed in. To promise you wont change anything, you can pass a reference to const
void someMethod(const sf::Texture& Texture);
but then you are limited to using methods of sf::Texture that are const qualified for example
unsigned int GetWidth () const
however you would not be allowed to call
void Update (const Uint8 *pixels)