Read the instructions starting on page 42 to access the Media Server settings on your router.
https://dlcdnets.asus.com/pub/ASUS/wireless/RT-AX58U/E16133_RT-AX58U_UM_1119.pdf

Find the Media Server Name and Device Name. You might need to rename it to remove any spaces or dashes.

If the Media Server Path setting is set to “All Disks Shared”, the share path will probably simply be “\\<MediaServerName>“ or “\\<MediaServerName>\<MusicFolderName>“.

You can also use the router’s IP address: “\\<IP Address>“

I’m using the Media Server method. Media Server Name is what I don’t understand. Is is the name of the SSID I’m using? Or is it simply the name of my router which is MYASUS? Also, what should I be using? Media server or Samba? 

Media Server should work. What does it say next to Media Server Name?

I used Media Server and did get a connection using the IP address. I’ll go in and check the name. I need to understand this. Thanks! 

The name is the actual model number of the router. It is greyed out.