As transactions clear your bank, or the account you can mark them cleared by selecting them and then tapping on the checkmark in the icon bar:
This will toggle the Y or N which is present int he second column of the account's transaction list. Alternatively you can Edit the transaction and check or uncheck the Cleared field.
To delete all the transactions marked as having cleared, and post them against the first transaction (which should be the Balance transaction you entered in the Getting Started section) you use the RollUp Cleared Entries in the File menu:
This will then ask you if you are sure. If you click Yes, then the transactions are posted to the first transaction in the account and are removed.