Metadata Container is a collection of Metadata Objects. Each object holds the list of their fields and relations (foreign keys).

public void FillMetadataContainer()
{
	// create table
	MetadataObject tableOrders = 
		queryBuilder.MetadataContainer.AddTable("MySchema", "Orders", false, "MyDB");
	tableOrders.Fields.AddField("OrderID");
	tableOrders.Fields.AddField("OrderDate");
	tableOrders.Fields.AddField("CustomerID");
	tableOrders.Fields.AddField("ResellerID");

	// create another table
	MetadataObject tableCustomers = 
		queryBuilder.MetadataContainer.AddTable("MySchema", "Customers", false, "MyDB");
	tableCustomers.Fields.AddField("CustomerID");
	tableCustomers.Fields.AddField("CustomerName");
	tableCustomers.Fields.AddField("CustomerAddress");

	// add a relation between these two tables
	MetadataRelation relation = tableCustomers.Relations.Add();
	relation.ChildSchemaStr = "MySchema";
	relation.ChildDatabaseStr = "MyDB";
	relation.ChildNameStr = "Orders";
	relation.KeyFields.Add("CustomerID");
	relation.ChildFields.Add("CustomerID");

	//create view
	MetadataObject viewResellers = 
		queryBuilder.MetadataContainer.AddView("MySchema", "Resellers", false, "MyDB");
	viewResellers.Fields.AddField("ResellerID");
	viewResellers.Fields.AddField("ResellerName");
}

To add case sensitive object, database, schema or field names you should quote them according to the quotation rules of your database server.

Active Query Builder allows adding fields for each database object not right after it's addition to the Metadata Container, but fill them when they are used in some query at the first time using the QueryBuilder.MetadataContainer.ObjectMetadataLoading event handler:

void MetadataContainer_ObjectMetadataLoading(MetadataContainer sender, MetadataObject metadataObject)
{
       if (metadataObject.NameStr == "Orders")
       {
               MetadataFieldList fields = metadataObject.Fields;
               fields.AddField("Field 1").FieldTypeName = "nvarchar";
               fields.AddField("Field 2").FieldTypeName = "int";
               fields.Loaded = true;
       }
}

You can remove unwanted fields after they were loaded from the database in the QueryBuilder.MetadataContainer.ObjectMetadataLoaded event handler:

void MetadataContainer_ObjectMetadataLoaded(MetadataContainer sender, MetadataObject metadataObject)
{
       if (metadataObject.NameStr == "Orders")
       {
               metadataObject.Fields.Delete(metadataObject.Fields.FindFieldByName("Freight"));
               metadataObject.Fields.Delete(metadataObject.Fields.FindFieldByName("ShipVia"));
       }
}