FROM Customer c
INNER JOIN Order o
ON c.CustomerID = o.CustomerID;
But I'd change a few things.
1) Make your table name plural:
: this reflects that the tables contain multiple items rather than a single Customer or a single Order.
table to just
table. You can't mix 'em up because you have to specify the table they come from Via FROM or JOIN, so why duplicate information via the column name?
Your JOIN then becomes:
ON c.ID = o.CustomerID;