Dropbox

How can I delete the images currently in it

While viewing the list of images or files within the DropBox app, place your finger on the file you want to delete and swipe to the right. Afterwards, tap on the Trashcan icon to delete it. If you want to delete several files, tap on the 3 dots in the upper right corner, then tap on "select". Now tap on the squares in front of each file you want to delete. Afterwards, tap on "Delete" in the bottom left corner.

Also make sure you turn off Camera upload or any pic you take with your phone will ready itself to upload to Dropbox once you turn WIFI on. I leave it on because it gives me a great place to store my photos if I should choose to get rid of anything on my phone but not permanent. It will be in Dropbox. :)