Marginal rate of substitution
There is more than one indifference curve. There is one belonging to every utility level. So for any utility level $c$, the points $(x,y)$ that satisfy
$$2\cdot \sqrt{x} + y = c$$ are an indifference curve.

For example let $c = 2$. Can you find a point $(x,y)$ that satisfies
$$2\cdot \sqrt{x} + y = 2$$
and is on the $y$-axis or the $x$-axis?