Picross puzzles are solved by filling in all squares using the hints on the left and top side of the grid. A number will indicate how many consecutive squares are filled in for that row or column. If there are more than one number, then between each number there must be at least one empty square. You can mark empty squares with an X. If you have any Pokémon in your party, then you can use their skills to help solve the puzzle. There is no penalty for filling in an incorrect square, but there is no indication that it is wrong. Each puzzle has missions that reward Picrites when the conditions are met after solving the puzzle. Any missions that are missed can always be retried by solving the puzzle again.
Puzzles can be logically solved without guesswork. If you are having trouble, you can use Blue Force to highlight rows or columns in blue that have a square that can be filled in or marked with an X.
A 0 means a row or column is completely empty and a number matching the dimension of the puzzle means the entire row or column is filled in.
A single number that is greater than half the width or height of the puzzle has squares in the center that can be filled in. For example, consider a 10 × 10 puzzle with a single hint of 6 in one row. If you look at all possible placements of 6 filled squares in that row, then the two middle squares are always filled in. You can quickly see the overlap by comparing the two placements where the 6 squares start from the left side and the 6 squares end on the right side.
Filled in squares on the edges can help with solving the first or last number hint going the other direction.
If the number of unknown squares in the row or column that are between X's or an edge is less than all hint numbers for that row or column, then you can rule out those squares being filled in.