The ParkZone J3Cub is clearly identified by the manufacturer as being for intermediate flyers, it is not intended for beginners. If at all possible, set it aside and get the HobbyZone SuperCub. The J3 has some traits that make it less than ideal for flying. The SuperCub corrects all of those traits, and gives better performance.
If you are determined to learn with the J3, do the following modifications: 1) change the prop to the High Pitch Prop. This will greatly improve the take-offs; 2) add a tail wheel. DuBro makes a nice steerable one, or get the non-steerable replacement wheel for the Aerobird Challenger and attach it to the front of the tail skid. The tail wheel is a must to control the plane's tendency to do ground circles when attempting to take-off; 3) Change the wheels to larger ones, preferably 2" diameter. Again, th8is will decrease the tendency to ground-loop and prevents the prop from striking the ground on take-offs and landings. 4) fill the nose of the plane, between the firewall and the battery box, with expanding foam. Remove the motor wires and insert a large straw (like McDonald's) through the firewall and past the battery box. After the foam has set, trim the straw as needed to allow a path for the wires.
Go to RCGroups - electric flying beginner forums and look up the sticky from AEAJR about tips for beginner flyers:
http://www.rcgroups.com/forums/showthread.php?t=355208