How do I use the Trim feature?

Hello

I would like to make a part impression and I know that it is possible with the trim function (Edit/Trim)

But I don't know the details of the manipulations to be done. Could you help me?

Thank you

Thomas

Hello

As shown in this video. It's in English, but understandable...

http://www.youtube.com/watch?v=WOjDDRgwHzg