You need to let the jars cool on their own, preferably for at least 6 hours, and hopefully overnight.
Jars need to cool before inoculation because spores are killed by excessive heat (such as the temperature inside a PF-tek style jar after being boiled for 45 minutes to an hour). So, you need to let the jars cool on their own, preferably for at least 6 hours, and hopefully overnight. It is recommended to cool jars directly in the pot in which you boiled them, since this will reduce the chance of airborne contaminants landing on the lids of your jars (contaminants can't land on jars that are kept cooling in a covered pot). A jar cool to the touch may still be too hot inside for spore life, so do not judge the internal temperature of the jars by touching the glass. And do not open the jars for obvious reasons. FINALLY, DO NOT COOL JARS UNDER COLD WATER OR IN THE REFRIGERATOR. Cold water/air hot glass = cracked glass and unusable substrate. Trust us on this one, the glass WILL break if made too cool too quickly. A mantra in this hobby - "patience, young jedi."