Pour some sweetened condensed milk into a glass. Personally, I like this drink very sweet. I'd start with 2 tablespoons and see how you like it.
Boil some water. Add 2 tablespoons of coffee to the filter, screw the top on and set it on top of the glass.
Fill the filter all the way with boiling water, place the lid on, and allow the liquid to slowly drip into the sweetened condensed milk. This will take several minutes.
Once the coffee has finished dripping, stir the mixture together and pour it into a fresh glass over ice. Enjoy!