Johna, welcome to WikiTree. Here, everyone has a profile so you don't want to change your profile to make it your spouse's profile. Just add a new profile for your spouse. If you click the Edit tab on your profile, you will see a link to Add a Spouse. Click that to do it.
After you add your spouse's profile, you will be able to click the Edit tab on it to add your spouse's parents, siblings, etc. ... and now you're off and running on adding all your spouse's tree branch.
If your spouse wants to work on WikiTree, you can enter your spouse's email address on her profile (but it has to be different from yours) and WikiTree will automatically send your spouse an invitation to join. After that, you can can make each other co-managers of each of your own profiles if you wish, and also co-managers of all profiles in either or both of your families.