1) Move the cursor to "Effects" window and click on the command "Sine Plasma" in "Generate" group.

2) Now we can edit this command in "Controls" window. Let's try. Set values of "Period of X Sine" and "Period of Y Sine" to 4.

3) Then click on "Add" button. "Sine Plasma" was remembered in "Script" window.

4) Then, again choose "Sine Plasma" in "Effects" window and set such parameters:

Other parameters left without changes.

5) Then click on "Add" button.

6) That's all, now your image is ready.

Hint:  Try to experiment with parameters of  first "Sine plasma". For  that  simply click on  "Sine Plasma" in "Script" window.