You are logged on to the database as a database user.
You have the INDEX privilege for the table.
The database is in the ONLINE operational state.
In the context menu of the table to which the index belongs, choose Definition.
In the context menu of the editor window, choose Edit.
Change the index definition.
Note
To display the definition as an SQL statement, choose Export SQL in the context menu of the editor.
In the context menu of the editor window, choose Alter Index.
SQL Reference Manual, ALTER INDEX Statement (alter_index_statement)