How to join to AVI ?
Click on AVI Join.
Little remark. The avi you want to join must have the same framerate. Or you will not be able to join them. The files must have also the same streams. For example, don't try to join one avi, that has a video and sound stream, with another one, witch has only video stream for example!
In fact, the avi you want to join must be as identical as possible.
Then, just select the first file,the second file and the output avi file name.
For example, if you have Film1.avi + Film2.avi = Film3.Avi, the Film3.avi file will be the merge between file1 and file2
Then, click on Join...