How do I build a read/write 4-nibble RAM memory system using flip flops? Currently, I'm learning about flip flops and how it is used in RAM to store memory so I'm trying to recreate the circuitry in Logisim.  I know the components I need which are address register, 4-bit data register, 1 bit read/write register and the actual 4 nibble RAM with its own address space and data space.  How do I create each individual pieces and put them together?
You need to put multiplexers and selector/decoders around your flipflops.

The read path needs to multiplex each nibble using the 2 address line.

The write path is selecting with these two address lines with nibble should be modified.