In FPGA there is special serial port which can transfer configuration data from ROM to SRAM. For organization of data. you can reference some FPGA books. Different architectures have different organization.
Try this book.. design warriro's guide to programming in FPGA.. there are types of FPGA programming which include SRAM and Anti fuse method.. i shall upload some materials and the book Design warriror's guide, if u really want it
several configuration mode, let's use Xilinx as example, I use SelectMAP mode to download fpga data, which I like it very much, because I can still use the COnfiguration port as regular CPU port after the FPGA is started.
I refer to use this because it allow software to online update the flash memory and online update the fpga