Querying Change Data Capture data
You use built-in table-valued functions (TVFs) as described in Books Online : Using Change Data (MSDN).

First you need to find the LSNs you want to use to filter the ranges you want to query. These LSNs will represent points in the log which you can correlate to datetime values. You can do this using sys.fn_cdc_map_time_to_lsn. Let's say you want to report on all the change data captured today:

DECLARE 
  @s DATE = SYSDATETIME(),                  -- start today at midnight
  @e DATE = DATEADD(DAY, 1, SYSDATETIME()), -- end tomorrow at midnight
  @sl BINARY(10),                           -- start LSN 
  @el BINARY(10);                           -- end LSN

SELECT 
  @sl = sys.fn_cdc_map_time_to_lsn('smallest greater than or equal', @s),
  @el = sys.fn_cdc_map_time_to_lsn('largest less than',              @e);

SELECT @sl, @el; -- start LSN and end LSN within today


Then you can use those LSN values in the cdc.fn_cdc_get_all_changes and cdc.fn_cdc_get_net_changes functions, depending on what you are after (let's say, for a table called dbo.floob):

SELECT * FROM cdc.fn_cdc_get_all_changes_dbo_floob(@sl, @el, 'all');

SELECT * FROM cdc.fn_cdc_get_net_changes_dbo_floob(@sl, @el, 'all');