The spouse and minor child (under 21) of a H-1B international employee who is changing status within the US must file concurrently for a change of status to H-4 unless they have independent non-immigrant status. Spouses and minor children not in the US should apply for H-4 visas at the US Consulate in their home country.
Please note that H-4 dependents are not eligible for work authorization and are not allowed to work. If a spouse is currently in J-2 visa status and is working, his/her employment must cease from the date the H-4 petition is approved. The fact that the work authorization card is still valid does not matter; if their visa status has changed to H-4 they are no longer eligible for employment authorization.