You must have an account with Islami Bank Bangladesh Ltd at first place.
Please click the link to know registration process (https://goo.gl/9dcMhA). After activate iBanking from branch, then install the app & activate your device (See the video https://youtu.be/F6K7hyJGOeM). For detail call at 16259 or email at support.portal@islamibankbd.com.