You mean which version of Tiled ? Just check in system if your PC is 32 or 64 bit and use the corresponding one
Edit :
So you can’t “just open” an image with Tiled :

You need to click New Tileset

And then choose your image as a Source, and give whatever name you want to the tileset.
And that’s it at this point you can get the ID of a cell just by clicking on it.

You can probably edit the tileset from here instead of going back to gimp but I don’t know how it works beyond getting tile ID