To use the dried Chipotles, toast them in a skillet first for a few minutes to wake up the flavour, then soak in hot water for about 30 minutes. You can use the water in what you are making, or freeze for another dish. Remove the chillies from the water, and then finely chop or purée into a paste, and use in your recipe. No need to remove the seeds.
Store dried chipotles in a sealed jar or sealed plastic bag in a dry, cool place for up to two years. Or, freeze them in freezer bags for several years.
The Aztecs inherited the smoking and drying technique, and called the peppers “chilpotle”. “Chil” was the chile; “poctli” meant smoked. Though “chipotle” means just “smoked pepper”, it is in practice applied to smoked jalapeno chile peppers. It is pronounced “chee — POHTE — lay”.