Big pan. Fill to about 2/3 with water.
Put a saucer upside down on the bottom of the pan.
Sit the pudding on the saucer. Construct a lid - if you don't have a lid that will fit over all that (maybe a wok lid would work?), use a big piece of foil, put the largest plate you have on top of that, get the foil to fill in the gaps.
Turn on the heat. When it comes to the boil, have a look to make sure the water isn't boiling so high that it is going under the pudding wrappings - if so, remove some water.
Turn the heat down to a visible simmer.
Look again in about 2 hours. If your 'lid' is working reasonably well, you may be OK, otherwise, top up with BOILING water.
Next year, use a Mary Berry recipe, or the recipe on the side of the packet of raisins, it's a lot less confusing than Delia.