How do I get ubuntu to make use of the swap file. It doesn't even use the full physical memory, it only uses 1.3 Gb of 8 Gb, and it doesn't make use of the swap file at all, even when it has detected that there is a swap file there.
If Ubuntu's only using 1.3GB of your 8GB of RAM, it probably doesn't need to use a swapfile.
Is there any reason you want it to? RAM is usually faster, I think.
If you start using more RAM, there's no need to worry -- Ubuntu will use swap space as needed.