Under the menu item "Community" you can start your own community and see all communities you have already joined. You can click on "Create community" in the top right corner. Then you can choose a community name and click on "NEXT". Now you will receive a link to your community. You can forward this link to all people who should join your community.
Currently you can only use the Mobile App on Apple devices. We are working on offering SPITCH on Apple devices for Mobile-Web as well.