Okay, so this is what I think you mean…
You have all the items stored in a database
You are able to display the items by creating and connecting to a dataset in a repeater
My questions at this point:
Does the database have a column to indicate whether the item has been selected or not? This could be a boolean (true/false) or a number field (if say there are 5 items)
Have you set up a way to select an item yet or are you just displaying them in a repeater so far? (a checkbox, button, etc)