How do i get this lighting effect? (icon by leukosia )

I'd ask the icon maker but I know I get annoyed when people ask me how to make my icons and I don't want to annoy people heh.

I used PSP8 and Animation Shop 3

PS: I checked the memories but nothing was specific enough. People name an effect but don't give the settings and I honestly am not smart enough to figure it out haha

 

Thanks!