Create a partition on /dev/sda:

# fdisk /dev/sda
    p (print partition table to see a summary of the partitions already present on /dev/sda)
    n (create new partition)
    p (primary)
    enter (default partition number - 6)
    enter (default 1st block)
    +65M (size of the new partition)
    p (print partition table to make sure no mistake has been made)
    w (write changes made to the partition table)

Use partprobe to update system’s awareness about the new partition:

# partprobe -s

Create Linux SWAP filesystem type on the new partition /dev/sda6:

# mkswap /dev/sda6

Write the swap partition UUID to /etc/fstab to make it persistent across reboots:

# blkid | grep /dev/sda6 >> /etc/fstab
# vi /etc/fstab
    [...]
    UUID=UUID_of_/dev/sda6 swap swap defaults 0 0
    [...]

Mount the new swap:

# swapon -a

Check the swap:

# blkid | grep swap
or
# swapon -s
or
# cat /proc/swaps
or
# free -h