newbie needs dataset-sqltable update code

I have dataadapter and dataset that reads/writes to SQL tables.
I can read. I can create "new" records.
However, I have not been able to master the "updating" of an existing row.
Can someone provide me specific code for doing this please or tell me what I doing wrong in the code below.
The code I using is below. I don't get error, but changes do not get written to SQL dbase.
For starters, I think I "not" supposed to use the 2nd line(...NewRow). I think this is only for new row, not updating of existing row - but I don't know any other way to get schema of row.
thanks to any who can help

Dim drow As DataRow
drow = Me.dsRequests1.Tables("REQUESTS").NewRow
drow.BeginEdit()
drow.Item("Request_Name") = Me.txtRequestName.Text
drow.Item("Request_Comments_Txt") = Me.txtRequestComments.Text
drow.Item("Requestor_Contact_Id") = Me.txtRequestor.Text
drow.Item("Request_BigX_Status_Type_Cd") = Me.ddlBigXStatus
drow.Item("Request_Action_Type_Cd") = Me.ddlRequestActionRequested.SelectedItem.Text
drow.EndEdit()
Me.DaREQUESTS.Update(Me.dsRequests1.Tables("REQUESTS"))
Me.dsRequests1.AcceptChanges()You're right
NewRow is only for new rows,
To update an existing row you should find the row in your dataset/datatable - using your table's primary key and find method or by index - change it's values , and update your dataset/datatable
Something like this (if you're using a typed dataset)

Dim drow as DataRow = dsRequests.Requests.findbyprimarykey(myParimaryKeyValue)
drow.property = newValue
daRequests.update(myTable)

hth