@Christine Ambie Wilson
Just go to the "Family Members" Section; and, select "+ Add Spouse".
That creates a new/another "Couple Relationship" (where there are yet, NO Children added).
I hope this helps.
It's a while since you asked this question, but there is a little more information that may interest you.
If you are adding a second spouse, there will be different relationships created in the family. There are different ways to show the children of the household for example related to the new parent, i.e you may wish to specify that the child parent relationship is a biological/a step relationship and you can even change relationships to show that a child was adopted etc. Here is an article from the FS Help Centre that explains how you can show these different relationships in Family Tree.
If the child is attached to the wrong parent, you can also correct the incorrect child parent relationship that has been created. The following article explains how you do that: