Entering Partner details is not possible?
This happens because the marital status is set to "unmarried". As long as that is the case, you cannot enter partner details.
Here is how to fix it:
- Go to Employees
- Select the employee
- Click on Edit next to Personal
- Change the marital status (to e.g. "married")

5. Enter the marriage date and Save
Now you can fill in the Partner details in Family.