TBH I'm not 100% sure on what it 'should' be doing but regardless you can set it up however you want. Looking at your current usage you have tons of free RAM but if you want to set one up anyway then it's pretty easy.

Usually Linux uses a partition as swap (rather than a file as Windows does) but for convenience in an already running system I would think that a file is easier to set up.

So as an example I will make a 1GB swap file in /mnt (which as you can see resides on your 4G SSD but you could put it somewhere on your root device if you'd rather...)

mkdir -p /mnt/swap/
dd if=/dev/zero of=/mnt/swap/swapfile bs=1M count=1024
chmod 0600 /mnt/swap/swapfile
mkswap /mnt/swap/swapfile
swapon /mnt/swap/swapfile

Then to make it remount swap on reboot edit /etc/fstab and the line:

/mnt/swap/swapfile    none    swap    sw    0   0