Data | Open A File/Session…
When you choose this option you will be prompted to select a file to load into MEGA. You may hit cancel if you don’t wish to load a file yet. Once you have selected the file MEGA will determine the type of file you have selected by it’s extension (eg. .nwk, .meg, .msdx, etc.)
If there is any issue with the file such as improper format of the data, or the data being corrupt MEGA will alert you of the issue.