Basically, to insert musical notes into Microsoft Word, you need to use the symbol codes. The way this works is that you type the symbol code, and then immediately hit ALT+X on the keyboard. This will tell world to interpret the proceeding text as a symbol code, and it will produce the requested symbol.
Here are the codes for the musical notes:
Quarter note: 2669
Eighth note: 266A
Beamed eighth notes: 266B
Beamed sixteenth notes: 266C
Music Flat Sign: 266D
Music Natural Sign: 266E
Muisc Sharp Sign: 266F
So, to make a quarter note, you’d type 2669 and then hit ALT+X on your keyboard.
For more advanced musical symbols, you’ll need to use a musical symbol font. A good listing of musical fonts can be found here.