a) are you using PHP or another server model (e.g. CF)? Please always mention this to help someone provide an adequate solution.
b) when you say "dynamic text session", does this mean you want to display a certain session variable like e.g. the "kt_login_user" variable defined in ADDT´s "Login Settings" ?
Well, if it´s PHP and my assumption b) is true, you might want to add
somewhere within the generated PHP block at the page´s top.
(and not related to ADDT) problem with making a page detect the session is :: ADDT´s forms and list always catch them well by default, but manually created PHP pages usually require you to add the "@session_start();" call in order to activate the session detection.