Wait until your baby sits independently with a steady head, usually by age one....

https://www./parenting/when-can-a-baby-go-in-a-bike-seat-an-age-by-age-guide/

Wait until your baby sits independently with a steady head, usually by age one. Choose front mounts for interaction, rear seats for stability, or trailers for reclining safety. Always confirm neck strength first. Helmets are non-negotiable every ride!