Hi there, and welcome to the Guild!

There are a few ways to create elevation with Photoshop. I don't know if there are any tutorials specifically teaching how to use real-world elevation data with Photoshop, but I can point you towards a couple that deal in techniques that could be adapted for such a thing.

How well do you know your way around PS in general? I can try and go into a bit more detail if you're not too familiar with the software, but here is a short version of my initial thoughts.

The first is the classic Saderan tutorial. The part you'll want to focus on are the Step 3: Land, and Step 4: Mountains. They will go a bit more into detail on how to use the Bewel and Emboss layer style to create a nice 3D effect for your terrain.
What you'd basically want to do here, is use the real world height map as the layer mask, instead of creating one from scratch.

Here is another great little tutorial buried in the Guild archieves. Again, you'll basically want to skip the height map creation part of this one and use the real world data instead, and move straight onto rendering the terrain.

I don't know how well these would serve in terms of making the map as realistic as possible, as I don't really know what your goals are. If you are wanting to represent reality as accurately as possible, it might be that Photoshop isn't really your best option here. Realistic maps are really not my wheelhouse so I could be talking right out of my arse here, but I think GIS or maybe Gaea are more what you're looking for? There also Wilbur that I know a lot of people use for elevation maps.

Hopefully someone a bit more knowledgeable sees this too! I'm strigtly a fantasy mapper, I do know my way around Photoshop pretty well at this point, but I don't know how well these would serve in terms of making maps truly realistic. If you are wanting to represent reality as accurately as possible, it might be that Photoshop isn't really your best option here. Realistic maps are really not my wheelhouse so I could be talking right out of my arse here, but I think GIS or maybe Gaea are more what you're looking for? There also Wilbur that I know a lot of people use for elevation maps.