trimming beginning and ending to get smaller clip

I'm sure this is easy, but after trying for an hour, not to me.

I want to import a 30 second video clip, specify a staring point at say 10 seconds and an ending point at say 20 seconds and end up with an edited clip that is 10 seconds long, consisting of the middle 10 seconds. Anyone want to explain to me how this simple task is done?

Thanks