The Plasma object inserts a plasma pattern in your scene.
In the Objects tab, double-click on the plasma icon or click it and draw where you want it on the edit area.
The plasma texture has a default size and color. You can drag and resize the object and it will repeat. Right-clicking the object and selecting Edit will let you change the specific settings for the plasma pattern.
Texture width/height
Size
Color shift
Color
Type
Color mode