You have to file application for the H-4 dependent

The H-4 dependent application is different from the H-1B petition. Form I-539 has to be completed and required supporting documents have to be submitted. Often than not, H-1 worker may file I-539 for H-4 dependents along with the H-1B petition. However, H-4 applicants can file I-539 anytime after H-1B worker's filing the H-1B petition, either during the pendency or after the approval of the H-1B.