To aid in soldering the new battery, be sure the solder pad holes are clear of solder. This way, you can insert the new battery leads and solder them in place.

To open the solder holes, open a safety pin and push it against the solder blocking the hole. At the same time, heat the same solder pad from the other side of the logic board. Opening the holes completely will require repeating this procedure several times from alternating sides of the logic board.

These holes are extremely small, so the safety pin will probably be too large to pass all the way through. Do not insert the entire pin through the hole -- only the tip of the pin.

You can also try entering the tip of the pin on the other side of the board to open the solder pad hole.