Place lids on jars and tighten by hand (not too tight) and then place the jars on the trivet in the Instant Pot.
Fill the pot with water up to about a half inch below the bottom of the lids.
Close the Instant Pot, set it to Sealing and cook on "Manual / Pressure Cook" for 35 minutes on High Pressure. Once cooking has completed, do a full NPR (natural pressure release).
Once the pressure has been fully released, open the pot, remove the jars carefully (they are extremely hot) and let them cool on a cooling rack or cutting board.
Once the jars are very cool to the touch, remove the lids (they can sometimes be difficult to remove, so be careful not to cut yourself on the lid).
Use a spoon to stir the Dulce de Leche until it is smooth.