To make fields mandatory or not you can do the following :
Click Options
Click System Settings
Click Mandatory Fields Maintenance
You then select the form you wish to edit and then click the 🖉 Edit button and then tick the Required Field box for those fields you want to be mandatory.
⚠️ Important: Only fields that sit within the main record can be made mandatory, and they will be mandated when the record is first saved - so be careful about the forcing the collection of data too early (such as DOB on an applicant record).
If you would like to explore enforcement of linked data, such as communication types and attributes, please speak with your Account Manager or Customer Success Manager.