Select File -> Import -> Import QIF File... and follow the instructions. QIF is a file format that might differ much depending on the software that saved the file. How much details you will need to provide about the file depends on ambiguity of the date format, how localised the file is, and how well accounts are defined. Securities, investment transactions, memorised transactions, budgets, and classes are not imported.

This function imports data files with clear text values in columns separated by a character (comma, space, tab, etc.), with a new transaction on each row. Select File -> Import -> Import CSV File... and enter details about the structure of the file you want to import. Transaction parameters can either be imported from a column in the file or a set to a specified value.