Identity column can be used for generating key values. To reset identity column you can use DBCC CHECKIDENT to manually set a new current identity value for the identity column.
DBCC CHECKIDENT(table_name, NORESEED | RESEED, reseed_value)
The following example forces the current identity value in the ArticleID column in the Articles table to a value of 5, the next row inserted will use 6 as the value
DBCC CHECKIDENT('Articles.ArticleID', RESEED, 5)