Alimony is paid by a spouse who has the ability to pay to a spouse in need of support for a period of time. Only people who are divorcing or are divorced can ask for and receive alimony.
If you’re filing a Complaint for Divorce, then the request for alimony can be made in that complaint. There are different ways to file for divorce, with different forms required. See the Divorce service for an explanation of how the process works and the forms you need to file for divorce and to ask for alimony.