The goal of Full House is to draw a path that passes through each blank square exactly once. The path can only change direction when it hits a dark circle, a square that contains part of the path so far, or the edge of the grid.
Start by clicking/tapping on an empty square and then click/tap on the same row/column to draw the path in a new direction.
You will win the puzzle when the entire board is filled with no empty spaces. You will lose the puzzle if no other valid moves can be made while there are still empty squares left.