Please try renaming the .skel.byte file to .skel. The .meta file is a Unity specific file and not necessary for opening the skeleton in the Spine Editor. You will also require the texture atlas.
The .skel file is an exported Spine skeleton. You have to open that via the "Import data..." menu item:
https://marioslab.io/uploads/screenshots/xORHPpoArF.png
Once the skeleton is imported, you also want to unpack the images in the corresponding texture atlas. You can do this with the "Texture unpacker":
https://marioslab.io/uploads/screenshots/Xb9rTeBG3c.png
Just set the .atlas file (might be called .atlas.txt if used with Unity), and set an output folder. Once the unpacking is complete, select the "Images" node in the tree view and set the path to the output folder you unpacked the atlas to.