Once the CPU is installed it is time to install the memory (RAM).
Installing memory in modern computers is far easier than it used to be.
It is even easier than installing the CPU!
Inspect the memory for any obvious damage.
Align the memory to the slot (there should be a small notch).
Insert the memory into the slot.
If you have SIMMS (an older memory, most new systems will use DIMMS) rotate the memory until it clicks into position. Wow, that was easy. Time for another cup of tea/mug of coffee before installing the motherboard to the case