Petitioning is relatively straightforward, and you may be aware of the link to the petition template on the Select Committee website here;
Petitioning against the Second Additional Provision – Committees – UK Parliament
There are also links to guidance and documents on this page;
(I’ve also attached the guidance on petitioning provided for the Hybrid Bill): https://merseymeadows.uk/wp-content/uploads/2023/07/HS2-Petition-Guidance.pdf