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That's a new one! Never knew we had to mount physical memory (RAM). Seriously, you just poweroff the server completely, disconnect the power cord, ground yourself to avoid static electricity, open the case, add the memory into the slots, close the case and reboot the server. At boot there could be a message on your screen asking you to confirm the change in hardware by pressing a function key. After that the OS will boot normally.
I think those are all the steps involved. No mounting whatsoever. Check after boot in a console if your memory is detected by using in a terminal: