The objective of Sudoku is to fill each row, column and sub-grid with exactly one of the possible entries (usually, the numbers 1-9). A conflict arises if you repeat any entry in the same row, column or sub-grid.
To enter a number in the grid, click on the number on the left, and then click on the empty box you want to place it in.
Please see the settings icon on the right side of the page for instructions on how to use the tools in the game
Go to the Sudoku puzzle here: https://www.washingtonpost.com/games/sudoku/