Writing 3 bytes data in EEPROM
If you're using XC8, include xc.h header file, and use the functions

eeprom_write( addr , data );


and 

data = eeprom_read( addr );


So, to write/read 3 bytes, just call these functions three consecutive times, with different addresses each time, of course. There's no way to write/read 3 bytes at once, if that's what you meant.