Or simply you can add a new layer, and add a Gradient > Radial. Then you put the first colour to white and the second to black, but the black one put it transparent ( puting it to 0 opacity). Then you click on the point where you want to glow something and you can adjust the glowing as the radius that you want. And that's all, I put here an exemple that I maded for Instagram of me doing a Lumos like in Harry Potter:
https://www.instagram.com/p/BrcuURyFEz_/?igshid=yr6wvjpbk5h0
(the page does not let me insert the image)
I hope it help you
