To add or subtract expressions, expand them to make their denominators the same. Least common multiple of $4$ and $2$ is $4$. Multiply $\frac{\sqrt{2}}{2}$ times $\frac{2}{2}$.
$$\frac{\sqrt{6}}{4}+\frac{2\sqrt{2}}{4}$$
Since $\frac{\sqrt{6}}{4}$ and $\frac{2\sqrt{2}}{4}$ have the same denominator, add them by adding their numerators.
