The non-PCB side of the encoder has a larger metal area on one side, that I didn't take a picture of, that lines up with the square area on the PCB side where the spring is located. Carefully align the two sides of the encoder, ensuring the wiper arms make contact with the encoder traces.

Gently press the two sides together so that the four metal tabs engage and hold the assembly together.

Ensure the PCB can swivel around normally like it did before disassembly and that all four metal tabs are properly engaged.

Insert the two JIS-000 screws into the encoder assembly using the PCB notch for better access.

Rotate the PCB so that the notch is aligned with one of the screws.

Insert the encoder assembly into the knurled outer ring. Take care to ensure the screws line up with the threaded holes in the underside of the knurled outer ring.

Tighten the screw that is currently aligned with the PCB notch.

CAUTION: Be extremely careful when rotating the PCB to align the second screw. The screw tends to bind on the PCB and can cause damage.