The Lucena position is the most important winning method in rook endgames. The white king is stuck in front of its pawn; the black rook is ready to check from the side.
First drive the black king one more file away: give check with the rook on the d-file.
The plan: the rook goes to the fourth rank (Rd4), the king walks out, and as the black rook checks from the side, the white king approaches the rook and the rook steps in between. This is called building a bridge.