Creating a transaction
Transactions can be manually created by navigating to the originating account and clicking on the 'Create' button.
You can then fill out some information such as the Account (where the money came from or is going), the Category (how the money was spent or received) and the Payee (the person or company that received or gave the money)
Importing a bank export
You also have the option of import a file downloaded by your bank. Many banks offer the option of downloading an ofx file containing all your transactions from an account.