You could use a drop down list with a sql query to the users with a where clause limiting the users to the site, or even use a uniselector as a single select or dropdown type, and use the UserID as the Return Column. Both of these would work fine, the only thing the uniselector will allow you to do that the dropdown list won't is have it able to select multiple ones. If you just want a display of the users, then use the uniselector and have a custom grid layout by following Kentico's documentation. Should be pretty straight forward.