Small zip archive listed as a schematic, named only M546B. The name gives no brand, board revision or document details, so the contents have to be checked before use. M546B may be a device model code, but that is not certain from the name. A schematic set like this is normally used to trace power rails, locate the charging and PMIC circuits and check connector pinouts. Compare the PCB markings with the drawings to confirm the match.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @phoneSchematics. Enginerys does not host this file.
How to open a .zip file
Compressed archive that every operating system opens without extra software.
Built-in OS tools7-Zip