Answer:
You need:
A metal ball.
Another metallic object, which will provide the extra electrons you need.
A negatively charged object.
Step 1: Take the ball you want to charge and put it in contact with the metal object.
Step 2: get your charged object close to the second metallic tool, on the opposite side of the sphere. That will cause the electron cloud in the second object to move towards the sphere, crossing it as long as the two are in contact.
Step 3. At this point you can detach the electron source from the sphere, and then walk away. The electrons will have migrated from it to your original ball, charging it.