Having 2 Activities running at the same time

This is getting really annoying, as I still can't get this working. I have 2 activities, 1st activity opens the camera on clicking an imagebutton, the user takes a photo and the image gets placed in the imagebutton. The 2nd activity changes the background image when a button is clicked. Currently, only the camera application is working as its set as the LAUNCHER in the manifest. I would like to know what INTENT code I add on the MainActivity (1st activity) to make the second activity work. If someone could just possibly post a link or the code of having 1 activity launch another activity, I would be just as happy. Thank you :)