Rebuild index in table with many values

I'm junior DBA ,have table with 11 million values ,one of the indexes is like :

CREATE NONCLUSTERED INDEX [ix_mytbl_mycolumn] ON [dbo].[myTbl] 
(
    [my_id] DESC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON, FILLFACTOR = 80) ON [PRIMARY]
GO

For rebuild this index need only

ALTER INDEX [ix_mytbl_mycolumn] ON [dbo].[myTbl] 
REBUILD;

or with big tables need to prepare something.And also one question in this table I have some columns with asc index and some with desc , can be any problems after rebuild all indexes in this table? (ex.: slow select/insert). Is good idea to rebuild this index?