Depends on how dark the pencil marks are, could attempt to use an small eraser to rub the marks out.
In the future, use a water-soluble marker or thread/fishing line to grid
I recommend anyone just starting out to purchase a small sized kit say 5 x 7 finished size on 14-count aida cloth. In general with kits the aida cloth provided is too small to fit into a large hoop that accommodates the entire finished size. So I would also recommend purchasing a 10-inch plastic hoop and a 15-inch x 15-inch piece of 14-count aida cloth. This way the cloth will fit into the 10-inch hoop with enough material surrounding the finished work that you will not have crease marks from either your hands or the hoop. A hoop keeps your work clean and it is easier to find the center by folding the material and using a pin to mark your spot.
To remove pencil from aida cloth I recommend using a solution of 3-tablespoons of lukewarm to cold water with 2 to 3 drops of a clear liquid dish soap and 1-teaspoon of rubbing alcohol. Using a soft clean toothbrush dab into your solution and delicately brush the pencil mark. Rinse thoroughly with clean cold water and place onto a towel to dry flat. If once dry the stain is not removed repeat.
Do NOT put it in the washing machine! Get ahold of some newborn baby laundry detergent and a CLEAN bucket. You want to put a little bit of baby laundry detergent and lukewarm water into the bucket, put your piece in, and swish it around gently. Then take it out and rinse for at least 3 minutes. Lay it between two towels to dry, then iron on low to get the wrinkles out.
I personally wouldnt recommend you using machine because the picture might get damaged... I always wah it by hand, crefully, and then let it dry al the air
chekccard