The lens is VR 'stabilized'. You should expect, at the minimum, to be able to shot handheld at 1/500sec at 500mm. Try testing what you can do after various focal lengths and slower shutterspeeds to identify the slowest you can reliably shoot handheld. Use this knowledge in selecting your exposure settings.

To the extent I have learned PSE, I used my own 'real' images and utube to find examples of how-to actions. Assuming you subscribe, you can also find examples in the 'support' videos for learning on Adobe.com. It can take a while to find an example and then a while to learn to do it yourself, but going forward, each time it gets easier to perform the processing.

As others have said, the high ISO is the killer here. I would practice handholding while bracing if possible. I use the Nikon 200-500mm for about 90% of my photos, most at 500mm. I can shoot down to about 800/second hand held and lower if needed with care. I'm soon to be 69 and use the D850 with 200~500 like a barbell every morning and evening. It makes carrying and shooting the combo much easier!
Crop however YOU like by the way!! Don't worry about the one third rule! That's just silly! Yeah, sometimes it works, but it's NOT carved in stone!!

Here is an edited suggestion for you.
It's a very quick edit (5 minutes) so it's not perfect at all, but just to give you some idea about cropping (note that I retained the 6x4 format) and removing some of the distractions, and also darkening the foreground grass area a bit.
To do this edit I used my very old version of Photoshop (CS5), and then I did a single click using a NIK software preset to boost the colour.

Also, as someone else suggested, drop that ISO down as much as possible to reduce the digital noise (to IS0-100 when you can get away with it - and a lower ISO also gives a more vivid colour resolution - but around ISO-400 might be needed in your example here if the ambient light was quite low), and increase the exposure time to about 1/500 sec or so to compensate. You can also tweak the exposure a bit as needed in Post Processing.

When opened, the image improves. This is because the JPEG was not created using the sRGB colorspace. That's an error in your workflow that can be difficult to overcome when using PhotoShop to create JPEG output files and seeking to retain the EXIF. You'd be better served learning, at the minimum, to use the LR Export to create your output files.

The image is a relatively static subject, at a relatively high shutter speed, resulting in a higher ISO due to the low light, with a lens with a maximum aperture of f/5.6. Shooting slower at say 1/500sec could allow for cutting the ISO in half with no material change to the ability to 'freeze' this static subject. To the extent possible: always seek the lowest ISO possible for your images.

The digital noise is the primary issue. The links below are written for LR, but apply to similar tools in PS. In PS, you might 'mask' the fox and isolate that layer from the background. Then, better process the luminance noise (the black specs) of the background layer. The fox looks good where the noise is predominate in the background. The fox, though, could be better sharpened. In PS, then sharpen the isolated fox layer. Once you master this layered-processing approach, you can judge if capturing at a lower ISO is better than the level of effort in post.

Also in PS, remove all the grass that covers the fox. Everyone will have a different level of tolerance / level-of-effort on which to remove. I'd definitely remove everything covering the body in the foreground and the long yellowish grass that goes over the head above the animal's left eye.

Links:

Basics of noise processing

Basics of Lightroom Sharpening