In some cases, you may want to copy a file from an existing channel to another. This will save you the trouble of having to re-upload the file from your computer.
The Files Panel makes this task a breeze. Here's how:
1) Open up the Files Panel by clicking the Files button on the left.
2) Next, go to the channel you want to copy the file from. Then, drag and drop the file into the Files Panel.
3) Take the file you just added to the Files Panel and drag and drop it into the other channel.
Voila! You've just copied a file from one channel to another.