Editing recording of piano

I’m trying to make a cd of some songs I wrote on the piano. I have a standup, Baldwin Hamilton. I’m using a Shure 57 dynamic mic, and presonus audiobox. I have the piano open at the top, with the mic at the low end, pointing to the right, positioned as close to the hammers as it can be without touching. It’s all covered in several blankets to contain the sound. This specific mic and technique were recommended to me by someone at the local music store who actually knows what they’re doing and has recording many pianos . . . He said I needed to equalize the recording, and compress it several times over. I know the attached file is not the highest quality, and I know the basic rule of song recording is to start with the best quality possible, because you may not be able to improve it very much by editing. This file has not been edited. I’ve messed around with equalizing (which made the file very, very quiet) and compressing (which made the file super fuzzy - it sounded like it was raining)
I’m not expecting to get a professional sound in the space I am playing and with the equipment I am using . . . but any tips are welcome! (P.S. Talk to me like I’m a five year old. I know NOTHING about editing music, despite watching many, many videos on youtube.)
Thank you!

Does you mic lead have a big, 3 pin (XLR) connector on the end, or a 1/4" jack plug?

This is an XLR plug:

3 pin XLR cable.

When setting the recording level on the Presonus audiobox, you should play loudly, and gradually turn up the mic level until the “clip” LED just comes on, then back-off the mic level just enough so that the LED does not come on. Did you do that?

The reason that I ask is that the main problem with the recording is the amount of background hiss. There’s a lot more hiss than I would expect from that hardware.

I just tried that. The hiss got quieter, but the entire recording got quieter too, so proportionally, I’m not sure that changed it that much.
I just realized that I had the “48V” button pressed in. I was using that with a different mic that I was told needed it. I tried recording without that button pressed in and the hiss seems much quieter. The recording is attached. I’d still like to improve on the quality… I tried compressing, and it sounds like it’s raining. I was told I need to compress several times over in order to get the best quality, but is there another effect that has to be applied as well in order to reduce the hiss that the compressor makes? Thank you.

Could you post in a higher quality format, for example as a FLAC file. The forum should allow up to about 25 seconds in FLAC format before you hit the file size limit.

I don’t think that you need to, or “should” apply lots of compression as that will kill the dynamics in your playing.
The main problems, in terms of sound quality, are the amount of hiss and the rather dull timbre.

SM58s are known to be a bit “dull” sounding and not very sensitive (but they excel at handling loud sounds on stage environments, and are extremely rugged). The dullness can be compensated for (to a limited degree) by boosting the treble, but that will also increase the amount of hiss.

What is your other mic?