Your puppies should now be a little over 3 months old now which means they are just now gaining the ability to postpone elimination and wait for the correct circumstance to go. Don't get too frustrated, progress should come faster now. The key to efficient potty training is consistency and repetition. To encourage them to signal you is accomplished by using a phrase like "want to go outside?" before each trip, even while carrying them through the door, then repeating the phrase several times while outside and pouring on the praise and playful interaction during and after elimination. It helps if you use the same door to exit each time and that you repeat this scenario as many times during the day as possible. Going outside to play and still using the same approach will strengthen their association with the door. Some people like to use a bell that the puppies can ring as a signal. This works for some and still the key is showing them what act is desired and repeating it many times with lots of praise and enjoyable interaction.