It does not matter what temperature you add the DME to the water. The only thing that matters is that the DME is boiled for 10 minutes. Make sure when you add the DME the flame under the pot is off, that way you avoid burning the DME on the bottom of the pot.
Also, you will need to cool the wort to 70 degrees before you pitch your yeast. You will need a thermometer to make sure the wort is 70.