I thought it would be easiest to show you in pictures.
After you add your text, select the text layer and then go to the menu and follow the path Script-Fu>Layer Effects>Outer-Glow.
A box will pop up allowing you to select glow color, size, opacity.
This is what it looks like with the glow on.
I am using Gimp Paint Studio, if the configuration of my GIMP stuff looks weird to you. It's just GIMP with a bunch of presets added.