Start by peeling all your sweet potatoes.
Cut them into cubes that are roughly even in size.
Place the cubes in a a plastic bag that you can vacuum seal or use a gallon size plastic bag and try to get as much air out as you can.
Place into a 185 degree water bath for 1 hour. If they float, try to keep them under water using a small pot, just be sure the water level doesn't go above the max fill line for your machine.
Once finished, carefully remove from the water bath using a pair of tongs. Allow to cool for a few minutes before opening.
Ready to eat as is. Season with some fresh herbs. Or can be saved to be used with another recipe calling for cooked sweet potatoes.