I am entering starting balances in the balance sheet!
My company is starting new and have old debts to pay suppliers over a year,
Where shall I write them?
What name shall I give them?
If you are new to Manager, it is worth your while to read through the guides - these will avoid time-wasting on your part and on the part of forum users responding to questions which are dealt with in the guides
As for your question read this Enter starting balances
This is a confusing statement. If you are just starting your company, you should not have any accounts payable to suppliers. If you are migrating to Manager from another accounting system, the Guide @Joe91 linked to is relevant. https://www.manager.io/guides/7227 is more specifically tailored for suppliers.
On the other hand, perhaps you mean you will pay old debts over the time period of a year. That situation may involve entering purchase invoices with future due dates. See https://www.manager.io/guides/7189. Or it might involve creation of loan liability accounts. See https://www.manager.io/guides/9812 and https://www.manager.io/guides/10555.