Define a selection in your source audio file. See Define a selection
Tap on Copy 
to copy the selection to the clipbard.
Open 
the destination file.
In the destination file move the selector 
to the position you want to insert the clipboard.
Tap on Paste 
to insert the clipboard at the position of the start selector .
If you have defined a range (Start and end selector are defined) the range will replaced with the clipboard.