Assuming tempdb logical names are the defaults (which they likely are):

USE master;

GO

ALTER DATABASE tempdb

MODIFY FILE (NAME = tempdev, FILENAME = 'H:\SQL\tempdb.mdf'); -- as in 'c:\tempdb.mdf'

GO

ALTER DATABASE tempdb

MODIFY FILE (NAME = templog, FILENAME = 'H:\SQL\templog.ldf'); -- as in 'c:\templog.ldf'

After this you'll have to stop and restart your SQL instance.