This Forum is dedicated to Photoshop, not Photoshop Touch or Elements or some such.
Maybe this is a better place to get help with your issue:
Christoph, Almost, the companion apps are used in conjunction with Ps, but Ps Touch is not one of them.
DropboxIntegration are you using a Phone: http://forums.adobe.com/community/photoshop_touch_for_phone
Maybe I should stop replying to queries that concern items I’m unfamiliar with …
Download any images into your device using Dropbox's app.
Add images in PS Touch like you normally would with images that reside on the device.