A new clause or a new schedule is a proposal for a new standalone element of the bill.
If there’s nowhere obvious to put your amendment within the existing text of the bill, it might be better as a new clause (part of the body of the bill) or a new schedule (additional information at the end of a bill). Every schedule has to be mentioned somewhere in the clauses of the bill. So unless a new schedule is intended as a replacement for an existing schedule, it will be accompanied by a new clause or an amendment to an existing clause.
You can submit a new clause or new schedule in the same way as you submit an amendment.