Once the lockring is partially threaded in, insert the cassette lockring tool.

Tighten the cassette on the freehub body by turning the lockring tool clockwise.

The exact torque to tighten to varies by cassette manufacturer and model. Consult the cassette user's manual.

After finishing tightening, check the cassette for play by pulling up on the largest cog. If excess play is present and the cassette has been tightened to specifications, a spacer is likely missing.