Accessing someone's computer without their permission is illegal. So, us walking you through step by step into this persons computer, while implausible in possiblity in the first place, isn't going to happen here. Specific 'Help me hack so and so' questions aren't tolerated or answered here.
As far as locating evidence, if you say this person accessed you remotely, try locating a portion of their IP address and searching for files on your machine which contain this address, and possibly the event viewer, assuming you use windows. I don't see any other way to link this person with an action of such nature any other way.