It is not necessary but it will make no harm having it enabled. Instead, it will help you if ever needed more memory during a process...
To my opinion, it is better to have it on a usb stick. 128Mb is enough (this is my swap and never faced a problem with it) but you can go for the 256Mb option too...
Go [Blue] --> [Blue] --> Swap File Settings to create it and enable it. In the same panel, check "Enable swap at startup" to have it always enabled after a restart...
Then, in [Blue] --> [Yellow] --> [Red} you can check the global available memory...