1. To edit a template, use tools>General>Template. It's showing you this warning because this template is already enabled and pages are built using this template. If you change anything on this template, it will affect all other pages built using this template.
2. Can you elaborate more on which field you want to make as required? To make a field required you have to add a property required="true". In case you need to make any template properties required, you need to overlay the template properties and set that property required="true"
Hope this helps.
Hi @AvinashGupta01 - The field we need to make mandatory is a custom field, but the only choices I have on Tools>General>Template>ThisTemplate are Policy, Lock and Layout. How do I get to where I can add the property you mentioned? Thanks.