First, you need to add runat="server"
to your checkbox.
Second, you need to assign the checkbox an id that does not change. The repeater will take care of making the client-side id unique: id="chkDisplayTitle"
Third, you access items in the repeater like so:
foreach (RepeaterItem item in CourseAreaRptr.Items)
{
HtmlInputCheckBox chkDisplayTitle = (HtmlInputCheckBox)item.FindControl("chkDisplayTitle");
if (chkDisplayTitle.Checked)
{
//HERE IS YOUR VALUE: chkAddressSelected.Value
}
}