Hi wajid,
Good Job !!!
From hardware point of view, flash memory are available in different memory sizes and has different interfaces to connect it to micro controller. Generally some Flash memory have SPI interface, others have I2C interface & some have parallel interface. So, i suggest you to choose the right memory depending on the interface you have on the controller.Also, select the size of memory based on the maximum number of number of entries you want to save in flash memory.
From software or firmware point of view, you need to study the procedures on how to read & right data on flash memory. Further quries kindly post.
All the Best!!!