Please read https://www.manager.io/guides/9820 which is about journal entries, it for example explains that:
In Manager, most transactions are entered in other functional tabs, thereby automating many decisions about account posting and reducing errors. So journal entries are relatively few. Most record transfers between accounts. In fact, no transaction involving the actual receipt or payment of funds by a business can be recorded via a journal entry.
To enable functionalities such as bank and cash accounts, payments and receipts, customers and suppliers, invoices, etc you need to enable them through customize (bottom left of summary screen under settings of a business (see screenshot))
