It's generally not a good idea to start your symbol names with an uppercase letter and you should look at the difference between
That said, one answer to your question is to use
/@ below) to apply
Sqrt to both sides of your equation and add an assumption to
Simplify to allow it to simplify
x which is what I assume you want.
eqn = x^2 == 2 y;
Simplify[Sqrt /@ eqn, x > 0]
x == Sqrt Sqrt[y]
If you don't want this then
Solve[eqn, x], gives an alternative form as stated by others.