OS X macOS is quite efficient at memory management, and as said you don't really need to worry about it.
Along with other *nix OSs, it works on the philosophy that "unused memory is wasted memory" so it will tend to shift processes to otherwise unused RAM.
In recent versions of OS X/macOS(starting at 10.9) if you go into Activity Monitor, look at the memory tab. There is a graph at the bottom called "memory pressure." As long as it's green, you're fine.
Also, if you do have a burning desire to clear RAM you can open Terminal and type "sudo purge"(without the quotes) and hit enter. It will prompt you for your password(system password-you won't see anything appear on the screen as you type) and will clear out unused memory. Since about 10.10, the value of doing this has been questionable at best. My preferred browser is Firefox, and it's known for memory leaks. I tend to keep sessions open for a long time(basically I only close and reopen it when performance issues start hindering my utility) and I will occasionally execute a purge command in 10.12 for this reason. If you don't use Firefox, or if you do and close it every few days this isn't an issue.