Ok there are two issues here,
1. the product is crashing, so ok, lets maybe help on this one, you will to help all of us here to get this part sorted, can you post a bit more info on the PC you are using , make model, OS?, ect and maybe we can help on that one.
2. this product dose this easily, in video wave, and i do it all the time, so it dose work , but if your system is crashing then this may be part of why you cannot do this step.
you should sort out that first , then also have a look at the turorals that are listed under help in video wave, they will get you started on editing or cropping and joining videos.
can you add that info on your system and some of us users here can try to help you.