Peel sweet potatoes. Do this by either peeling raw potatoes with a potato peeler, or blanching in boiling water for 8 minutes, then pulling skins off (see video for demonstration). As explained in the above how-to article, I find that peeling raw potatoes is much more efficient.
Cut sweet potatoes into 1-1 1/2 cubes.
Loosely pack cubed sweet potatoes into canning jars leaving about an inch of headspace
Add salt to jars at a rate of 1/2 teaspoon per pint (1 teaspoon per quart)
Fill jars with water, covering sweet potatoes, and leaving about 1/2 inch of headspace
Wipe jar rims with a clean cloth to remove any debris
Screw lids and rings down firmly
Place jars into prepared pressure canner (i.e. water added, and rack inserted)
Secure lid with steam valve open, and heat over medium-high heat until steam begins to escape in a strong, steady stream
Continue to let steam escape for ten minutes
Close steam valve, and bring pressure canner to 10 psi for sea level. If you are at an altitude of over 1,000 ft, use this chart to determine your pressure need.
Once pressure is reached, Process pint jars for 65 minutes, or quart jars for 90 minutes
Remove from heat, and let canner return to zero pressure naturally
After pressure is dissipated, you may open the canner, and remove the jars if needed, taking precautions to prevent jars from cracking or breaking with sudden temperature changes. If the jars don’t need to be removed right away, you can keep them in the canner until they are completely cooled
After 24 hours, test seals, wash jars if needed, and store in a cool place out of direct light