Not sure what you mean by "I pulled up the database domain to adjust". Are you trying to alter the schema of the Database generated by the app? or are you trying to change the domain model from modeler?
What would be the best way to go about adjusting or changing it? - All the modification and changes for customizing the app needs to be done in Mx Modeler - Domain model (Add,Modify Entities like adding attributes, associations), Pages, Microflows etc. Say if you want to add a column in one of the tables in Database you would have to add that column as attribute to the Entity corresponding to that table in your Domain model.
Let me know if this answers your question or not. Good Luck!