The ATmega328PB contains 1 KB of data EEPROM memory. It is organized as a separate data space, in which single bytes can be read and written. The access between the EEPROM and the CPU is described in the following, specifying the EEPROM Address registers, the EEPROM Data register, and the EEPROM Control register.
See the related links for a detailed description on EEPROM Programming in SPI or Parallel Programming mode.