You can make lines or texts glow by using Glow (Outer).
Open ① Tool Selection window, use the ② Bucket tool, and ③tap the canvas to color it black.
Open the ① Layer window and create a ② new layer on top.
Draw some lines or texts with a white pen. (You can also use the Text tool)
Tap ①Layer window and add ②New Layer below the text.
Return to the canvas, open the ① Tool Selection window and select the ② Filter.
Select the ① Glow (Outer).
Drag the ①Slider left or right to adjust the radius.
Tap ①Color Picker . Drag the ②Slider left or right to adjust the color.
When finished, return to the canvas with ①✓ button.
Tap ①Layer window . Turn on ②Alpha Lock and color it with the airbrush to create a gradation like the finished image.
And you're finish. You can create neon effects like this with Glow (Outer).