If you used wire, loop the upper end down through the cap and wrap it around the other end of the hook so that no sharp end of the wire is exposed. If you used a paper clip bend the ends so that the y make loops. Put the lid on the bottle. Make sure the foil does not touch the glass when it deflects. The glass bottle protects the foil leaves from air currents.
Aluminum foil is used because it is light so it moves even with small electrostatic forces.
Slowly bring it up to the loop of the electroscope. Now touch the knob of the electroscope. Record your observations. Bring a charged golf tube near the loop. This time touch the loop with your finger while the golf tube is near the loop.