First. You NEED to be an e-5 with 4 years TIS. You also need to have gone to WLC, AND ALC (formally known as BNCOC) Once you have completed those tasks, you then need to talk to your schools NCO. After that, you drop your packet and wait.
I would, however, advise that you are at least a SGT (P) before applying to be a DS.
E-6, husband is also an e-6 and a DS