In this puzzle, the small molecule on the left is a ligand. It has a ring at one end that looks like phenylalanine, but then there's a part in the middle with a similar ring, except it's where the backbone of a protein would be. This is not a protein.
The molecule on the right is a protein. You'll notice it's colored green, while the ligand is colored red. (That's helpful, except for people with poor color vision.)
The goal of this puzzle is to connect the ligand to the protein with hydrogen bonds.
Click on the ligand to open the move tool. Then right-click and drag (or control-click and drag) on the cross to move the ligand closer to the protein.
You can also use the curved arrow of the move tool to tilt the ligand.
The arrows of the move tool can also rotate and tilt with just a regular click and drag.
Getting the red atoms of the ligand near the blue atoms of the two arginine segments of the protein is key to solving this puzzle. You can grab the sidechains and move them as needed.