Dependents in H-4 status may not be employed in the U.S., but they are allowed to attend a school/university.
If the employee and dependents are in the U.S., the department will instruct the H-1B worker and his/her dependents to prepare an I-539 application to change/extend their non-immigrant status. The H-1B worker will submit the application and supporting documents, along with a check to the department to include in the H-1B packet. OIS will file the H-1B petition and the I-539 application for the dependents simultaneously with USCIS.
If the dependents are outside the U.S., the department does not need to include any information about them in the H-1B packet. After the H-1B petition has been approved, the dependents may apply for H-4 visas at a U.S. consulate. In addition to the items mentioned in the Travel Outside the U.S. section, dependents should present a marriage certificate (for spouse) or birth certificate (for children) during the visa interview.