It will depend.
1. If you want to add some additional photographs to a ‘Postcard’ (Topic) you’ve already posted …. just click on the topic and then ‘add a post’ by dropping a new photograph into the Add to the Topic box and then click ADD THIS. You’ll find that when you now click on an image in the Forum the added photograph will be included in the display ‘Carousel’ of images.
2. If you have some new photographs of a different place or activity …. just ADD TOPIC in the Picture Postcard Group to start a new Topic and title and add your photographs and text as before.