Find the home position
Rest the middle finger on 5, which normally has a tactile marker. The index finger covers 1, 4, and 7; the middle finger covers 2, 5, and 8; the ring finger covers 3, 6, and 9. Use the thumb for 0 and the little finger for Enter when comfortable.
Keep the wrist neutral and move from the fingers instead of lifting the whole hand for every number.
Train accuracy before KPH
Begin with short vertical patterns, then add decimals, currency-style values, dates, and mixed lengths. Preserve leading zeros because they may be meaningful identifiers.
KPH is useful only beside accuracy. Repeated corrections or transposed digits can make a high attempted rate operationally expensive.
Use realistic but fictional drills
Practice invoice totals, product IDs, quantities, and tabular columns with synthetic values. Switch separators so tabs, spaces, and field boundaries do not become a surprise.
If your keyboard has no numpad, the number row can still build numeric accuracy, but the movement pattern is not equivalent to ten-key technique.