ALTER TABLE dbo.Employees 
ADD company VARCHAR (255) NULL;

####

Alter existing column:

ALTER TABLE Orders ALTER COLUMN shipToAddress1 VARCHAR (80);

ALTER TABLE Employees ALTER COLUMN address1 VARCHAR (80);

https://javarevisited.blogspot.com/2016/03/how-to-increase-length-of-existing-VARCHAR-column-in-SQL-Server.html#axzz7Lf1U1L2D