How do I find 4th root of x?

You can write the 4th root of x either of these ways

$$\\\sqrt[4]{x}\qquad or \qquad x^{1/4}$$

Using the calculator on the home page here you can enter x then press the ^y√x key then type 4 and hit the enter key. 

Or enter x then press the square root key (√x) twice.