Instruction of using ZX Spectrum's "Y-PLAYER" of MODs.

Hmmm. Pretty simple: use mouse. To reread disk move mouse into right side of a screen (a MENU will appeare) and chose required option. 
To load MOD click on the file with *.C extention (rest of files will load automatically). 
To PLAY/STOP use menu on the right side of the screen.

If You use an emulator, use some that has GENERAL SOUND card emulation. 
THE BEST WOULD BE "Z80 Stealth". 