This is an incredibly easy thing to google for. It is taking you longer to ask us than it is to ask google. For future reference, always google for how-to questions because the answers are out there.
However it is this easy:
EXEC sp_rename 'OldTableName', 'NewTableName';
And if you do not want to use the Stored Procedure, then right-click on the table in SSMS and rename it.