There is a Camera icon next to the "SEND" button, tap on it and you will be able to attach pictures from your device's Camera or Photo Library.
For the first time you tap on the Camera / Photo Library button, SLOWLY will request for permission, The permission request will only show up once. In case you missed that or changed your mind, please go to your device Settings, Looking for SLOWLY and grant the permission before continue.
This feature requires version 1.3.0 or above.
Right now you can only attach Images, up to 5 per letter.