Updating Table

I have following data table.

disp_id disp_date disp_tgasals disp_ccsales disp_locid
8 7/20/2004 <NULL> 114876 1
9 7/20/2004 <NULL> 25980 2
10 7/20/2004 <NULL> 43012 3
11 7/20/2004 <NULL> 38574 4

If i run the following sql statement

INSERT DisplayTran (disp_tgasals)
SELECT SUM(DailyTran.dlt_amt)
FROM DailyTran INNER JOIN
.GLedger ON DailyTran.dlt_glfk = GLedger.gld_pk INNER JOIN
Locations ON DailyTran.dlt_locfk = Locations.loc_pk AND GLedger.gld_locfk = Locations.loc_pk
WHERE (GLedger.gld_glno = '33101' OR GLedger.gld_glno = '33111' OR GLedger.gld_glno = '33121') AND (DailyTran.dlt_date = @dlt_date) AND (DailyTran.dlt_locfk = @dlt_locfk)
GO

Now the select statement will display data something like

5678
7890
8990
8909

and add it to the data table as disp_id 12, 13, 14, 15. Instead i want it to update the data table for ids 8, 9, 10, 11 for the disp_tgassals columns.

the biggest thing: change "INSERT" to "UPDATE"

and you need to specify WHAT to update

update TABLE
SET
(8,9,10)
VALUES
(Select... to get 8,9,10 results you want)
WHERE some condition (not necessarily needed )