If you have created a manual account, you can import transactions into that manual account via the Transactions page. Click on the Actions drop button and select Import Transactions from the list. The supported formats are .qif and .qfx files. The file size should not exceed 500K. Select the account you'd like to import those transactions into and click Choose File to select the file from your computer to upload. Click on the Import File button and you are done.
Please be aware that all transactions that are uploaded via this method will be imported as Uncategorized. Use the Bulk Editing feature to mass categorize similar transactions quickly and efficiently.