How Can I Preserve The Seeds?

Pick the seed pods when they are fairly dry. Put them in an envelope or other paper product so they will dry completely and be ready for planting in the spring.  Don't put them in a plastic wrapping as this retains moisture.

It is lucky you have two seed pods.  I should wait for the pods to ripen, then I would preserve the seeds from one in cool dry conditions, but I would immediately plant the seeds from the other.  I say this because some seeds lose their ability to germinate with time and do better when planted fresh.  I have no idea which category trumpet vine is in.  Be prepared to be patient.  I have planted different seeds and  nuts only for them to take so long to germinate that I forgot all about them and had to wait for them to grow big enough to identify.