1. First, from within TweetCaster select the menu and then Settings --> External Services:
2. Click on the "Timeline Marker" option:
3. If not already selected, select TweetMarker Sync (this should be the default):
4. With TweetMarker active, when you exit the app TweetCaster will set a TweetMarker on your timeline. If at any time you wish to jump back to your original timeline position/marker when going back into the application, please do the following:
a. Click and hold on the bird icon:
b. Select "Jump to TweetMarker" from the timeline options menu: