If you want to keep it simple, then use unsharp mask.
If you want to go one step further, then after applying it, go to Edit>Fade, and set to Luminosity Blend Mode. That way you won't have any color shifts on the edges.

It's possible to create a real edge mask (I describes how a while ago) but that may be a bit complex for now.

There are no Borg. All resistance is fertile.