In /etc/fstab you should have a line that reads
UUID=something none swap sw 0 0
If that’s not there you can add it by replacing “something” with the partition’s UUID that you’ll see using “sudo blkid” as plucky suggests. On my machine that returns
/dev/sda3: UUID="58e6b339-eac1-4acd-a9f2-d640f9b8b8bf" TYPE="swap"
If you use the UUID method in fstab, don’t include the quotation marks, just the UUID itself. The corresponding entry in my /etc/fstab is
UUID=58e6b339-eac1-4acd-a9f2-d640f9b8b8bf none swap sw 0 0
You’ll need to be root to edit /etc/fstab. Use “sudo nano /etc/fstab” or some other editor instead of nano like vi.